I saw an older colt lower that had something like this " law enforcement/government  use only" stamped on the right side of the receiver

It was at a gunshow but I didn't have the money to buy it.

I was thinking that would be neat to have on my a2 build.

Is there a specific name for this receiver or what do y'all call these?

I had some preban mini 14 mags that were stamped law enforcement use only on the bottoms. I guess it's called preban?

Both are post-ban, or, after the ban sunset.

Those markings are required by the now expired Federal Assault Weapons Ban September 1994 - September 2004)

I bought two Colt 6920's right when the ban expired and they have those markings.

As mentioned, these are not pre-ban markings. They were mandated on use for lowers that had pre-ban features but were available for sale to law enforcement agencies (and presumably export) during the ban. I generally refer to them as ban-era LE markings, although Colt continued to sell rifles with the markings for about 5 years after the ban ended.

They're an interesting reminder of a very weird time for firearms ownership.

i like them too.  

As stated before, they were manufactured for roughly 10 years during the AWB.  Colt makes a lot of firearms for LEO, and this was the period where flattop M4 variations really became popular with LEO.  

There are a lot of guys who think their marked lowers/guns are worth their weight in gold.  There are a lot of shyster gun hockers who are full of BS.

They are cool, some variations are more rare and have cool variations/markings.  They are worth a premium (some more than others), but they do not bring pre-AWB value to ban states.

In regard to the prospect of using this type of lower on an A2 build, I recommend not to do it. It would not look right or be correct.

What?  Come on…

Anyway….. if you want to be hyper OCD (I fall into that category) and/or pretentious about your A2 build, look for LEO marked lowers that comes with an AF forge stamped upper receiver.  They have authentic early A2 contours, and are really nice quality receivers.  

I like the LEO lowers in general, just because they are a little unique and the interesting are interesting.  I wouldn't hesitate to use them on any build for a little added character.

Yes, nice to have as a collector, but will not get you out of jail in communist states like CT or MA.