Thought you'd get a little more input over here, but the traffic volume is much lower than on the other forum.
Did find a little info in the archive. It only addresses the 6520, though.
http://www.ar15.com/archive/topic.html?b=3&f=118&t=270259
I'll post the main entry in case the link doesn't work for you.
Thanks go to Ekie.
1988-1989
GC 000550 can't make out the upper forge code, old style receviver extention nut/receiver extention/buttstock, slab side lower, small trigger pins, SP1 bolt carrier, blue extractor buffer, roll marked COLT'S FIREARMS DIVISION, no sear block
GC 000XXX can't make out the upper forge code, old style receviver extention nut/receiver extention/buttstock, slab side lower, small trigger pins, SP1 bolt carrier, blue extractor buffer, roll marked COLT'S FIREARMS DIVISION, no sear block, this one has a replacement grip
GC 000723 can't make out the upper forge code, old style receviver extention nut/receiver extention/buttstock, slab side lower, small trigger pins, SP1 bolt carrier, blue extractor buffer, roll marked COLT'S FIREARMS DIVISION, no sear block
GC 0054XX CM upper forge code, old style receiver extension nut/buttstock/nut, mag fenced lower, big pivot pin, small trigger pins, M16 bolt carrier, blue extractor buffer, roll marked COLT'S FIREARMS DIVISION, no sear block, barrel marked C MP 5.56 NATO 1/7 with a "2" at the front and the "0" for chromed lined at the nut, M4 feed ramps with the barrel extension marked but not the receiver
GC 0055XX CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, big pivot pin, small trigger pins, SP1 bolt carrier, blue extractor buffer, roll marked COLT'S FIREARMS DIVISION, no sear block
1990
GS 005600 or GS 005500 missmarked Carbine, only picture of roll marks, can see that it is a slab side lower
GC 006XXX can't make out the upper forge code, old style receviver extention nut/receiver extention/buttstock, slab side lower, trigger pin size (?), SP1 bolt carrier(?), blue extractor buffer, roll marked COLT'S MFG CO. INC., no sear block, green label box
GC 0065XX M4 marked barrel extention, M4 ramps in upper
GC 0066XX CM upper forge code, old style receviver extention nut/receiver extention/buttstock, slab side lower, small trigger pins, SP1 bolt carrier(?), blue extractor buffer, roll marked COLT'S MFG CO. INC., no sear block, green label box
GC 0067XX CM upper forge code, old style receviver extention nut/receiver extention/buttstock, slab side lower, small trigger pins, SP1 bolt carrier(?), blue extractor buffer, roll marked COLT'S MFG CO. INC., no sear block, green label box, manual dated 1990
GC 0068XX CM upper forge code, old style receviver extention nut/receiver extention/buttstock, buttstock not marked, slab side lower, small trigger pins, SP1 bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., no sear block, green label box, no M4 feed ramps, barrel marked C MP 5.56 NATO 1/7, peel washer
GC 007786 CM upper forge code, old style receviver extention nut/receiver extention/buttstock, , slab side lower, small trigger pins, SP1 bolt carrier ?, blue extractor buffer?, roll marked COLT'S FIREARMS DIVISION no sear block, peel washer
1991-1992
GC 00XXXX CM upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, big pivot pin, trigger pin size (?), SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., no pinned in sear block
GC 0087XX CM upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, big pivot pin, trigger pin size (?), SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on right side
1993- Sept 1994
GC 010272 this is a lower only, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, weep hole drilled, trigger pin size (?), marked COLT'S MFG CO. INC., sear block pinned in on right side
GC 01XXXX CMB upper forge code, mag fenced lower, small pivot pin hole, weep hole drilled?, large trigger pins, roll marked COLT'S MFG CO. INC., extention and upper marked 4, has M4 feed ramps
GC 015305 CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, weep hole drilled, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on right side, barrel marked C MP 5.56 NATO 1/7
GC 015XXX CMB upper forge code, roll marked COLT'S MFG CO. INC., has real M4 ramps, not the dremel jobs, "4" stamped about an inch or so above the gas tube, the barrel extension has the "4" on it as well, O stamped above chamber, no number stamped in barrel behind handguard cap
GC 0164XX CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, weep hole drilled, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on right side, blue label box
GC 165XX looks like sear block is pinned on right side only
GC 016614 CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, weep hole drilled (?), large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on right side, this one has a replacement flash suppressor and grip
GC 0172XX CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, weep hole drilled, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in right side, M4 feed ramps, barrel marked C MP 5.56 NATO 1/7
GC 017740 CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, no weep hole, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on both sides
GC 017774 CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, no weep hole, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on both sides
GC 018500 CMB upper forge code, old style receviver extention nut/receiver extention/buttstock, mag fenced lower, small pivot pin hole, no weep hole, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned in on both sides
Sept 1994-May 1995
GC 0193XX small pivot pin hole, no weep hole, large trigger pins (lower only)
GC 02091X upper forge code? old style receiver extension nut/buttstock?, new four position receiver extension, mag fenced lower, small pivot pin hole, weep hole drilled?, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., sear block pinned on both sideS?, M4 feed ramps, barrel marked C MP 5.56 NATO 1/7 and 02/95
GC 021031 an M4gery conversion, look like it has a sear block pinned in on both sides
June 1995-1997
LGC 003075 CMB upper forge code, old style buttstock, M4 receviver extention/nut/buffer, mag fenced lower, small pivot pin hole, no weep hole, large trigger pins, SPORTER bolt carrier, blue extractor buffer, roll marked COLT'S MFG CO. INC., no pinned sear block, blue label box, LEO roll markings, blue label, bolt has white paint mark, and carrier has shrouded firing pin, don't know if this bolt group is original (this particular Carbine has had the buttstock replaced with a modern M4)
1998-2001
LGC 017XXX black finish, forge code?, old style buttstock, M4 receviver extention/nut/buffer, mag fenced lower, small pivot pin hole, weep hole drilled, large trigger pins, SPORTER bolt carrier, extractor buffer color?, roll marked COLT'S MFG CO. INC, no pinned sear block, blue label box, LEO roll markings,
2002-2004
LGC 0XXXXX black finish, key hole forge code?, M4 receviver extention/nut/buffer & buttstock, mag fenced lower, factory front push pin, large trigger pins, bolt carrier?, black extractor buffer with gold spring?, roll marked COLT DEFENSE, no pinned sear block, blue label box, crush washer for flash, LEO roll markings, large reinforced lower receiver ring for the extention, barrel marked C MP 5.56 NATO 1/7
2005-2006
LGC 030000 Diemaco marked carrier, made in June of 2005
LGC 033686 black finish, forge code?, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, bolt carrier?, black extractor buffer with gold spring?, roll marked?, no pinned sear block, crush washer for flash, LEO roll markings
LGC 0342XX black finish, forge code forge marking is a capital "C" with an odd lopsided gemoetric figure, not the Cerro mark, that's for sure, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, M16 bolt carrier, black extractor buffer with gold spring?, roll marked COLT DEFENSE, no pinned sear block, crush washer for flash, LEO roll markings, barrel marked C MP 5.56 NATO 1/7, M4 feed ramps
LGC 034XXX black finish, forge code?, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, M16 bolt carrier, black extractor buffer with gold spring?, roll marked?, no pinned sear block, crush washer for flash, LEO roll markings, barrel dated 04/05
LGC 03496X COLT DEFENSE, LEO roll markings. M4 feed ramps
LGC 03498X keyhole forge code, COLT DEFENSE, LEO roll markings M4 feed ramps
LGC 03500X black finish, Cerro Forge Key Hole marked upper, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, M16 bolt carrier, bolt marked MPC, black extractor buffer with gold spring?, roll marked COLT DEFENSE, no pinned sear block, crush washer for flash, LEO roll markings, large reinforced lower receiver ring for the extention, M4 feed ramps, receiver ramp bare, black ejection port spring, barrel dated 06/05, hammer marked C
LGC 035006 black finish, forge code?, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, bolt carrier?, black extractor buffer with gold spring?, roll marked COLT DEFENSE, no pinned sear block, crush washer for flash, LEO roll markings, large reinforced lower receiver ring for the extention
LGC 036700 black finish, forge code?, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, bolt carrier?, black extractor buffer with gold spring?, roll marked COLT DEFENSE, no pinned sear block, crush washer for flash, LEO roll markings, large reinforced lower receiver ring for the extention
LGC 036941 black finish, forge code?, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, bolt carrier?, black extractor buffer with gold spring?, roll marked?, no pinned sear block, crush washer for flash, white sticker box, LEO roll markings, large reinforced lower receiver ring for the extention
LGC 036966 black finish, key hole forge code?, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, bolt carrier?, black extractor buffer with gold spring?, roll marked?, no pinned sear block, crush washer for flash, LEO roll markings, large reinforced lower receiver ring for the extention
LGC 03XXX black finish, key hole forge code, M4 receviver extention/nut/buttstock/buffer, mag fenced lower, factory front push pin, large trigger pins, bolt carrier marked C, black extractor buffer with gold spring?, roll marked COLT DEFENSE, no pinned sear block, crush washer for flash, LEO roll markings, large reinforced lower receiver ring for the extention, barrel marked C MP 5.56 NATO 1/7, M4 feed ramps but receiver ramps are in the white, no 4 marking on upper or extention, Diemaco bolt marked MPD 3021.