Many thanks to motown_steve, I now have an ARFCOM serial numbered Cav Arms Gen 1 lower.  Taken all the screws out of the stock, but it doesn't just pop apart like a cheap Chinese Army Factory #87 Airsoft plastic toy.  So - what's the best way to undo Cav Arms hard work of plastic welding the two halves together?

And for those of you wondering why I'm contemplating the best way to destroy a perfectly good lower, I refer you to Boris' thread:

http://www.ar15.com/forums/t_3_4/676733_Fruity_Ghost___DIY_100s_of_ARs_cheaper__faster__gentler_.html

Boris, of Shovel AK, Iron Glock, and now Fruity Ghost fame...

You forgot RPG shotgun.