Up until now I was under the impression that all Colt LEO Rifles had a sear block, either the pinned in type or the unmilled web. Funny thing, I popped open one of my 6721 LEO rifles tonight and was surprised to see that there was no block and the sear area was actually cut like an SP-1.
I am quite fond of the Colt 6721 and have collected a number of pre-ban and LEO rifles over the past ten years. Going through my safe and checking each, this is what I have found:
6721 Pre-Ban-
BD0001xx - Pinned in Block
BD0001xx - Pinned in Block
6721 LEO Rifles-
LBD0026xx - No Block/SP-1 Type Sear Area
LBD0045xx - No Block/SP-1 Type Sear Area
LBD0104xx - Unmilled Web Type Block
Others with Ser# > LBD0104xx - Unmilled Web Type Block
So it would appear that the original poster was correct in his statement " there may be more differences than meets the eye".
Pic of LBD0026xx showing SP-1 style sear area-
As a reference, this is the "Pinned" style block:
And the unmilled "Web" style block: