Well, .223 or rather 556 (same thing, but different).
The ARs are nice modular guns. Go for it.
There are several ones in .22LR AFAIK and of course adapter kits for putting .22LR mags in the mag wells of the standard rifles, but that is of course of no interest to you, as you are looking at a 22.
According to the ATF, Pac West Arms (PWA) produced 2,964 rifles in 2000. Only 2 in 2001. The PWA company is now defunct. Only 2,966 rifles built.
PWA also produced complete AR15s in the late 70's and early eighties and lowers in the nineties.
All pre-ban lowers have PWA with a circle around it stamped and under it is Milan, IL. 5.56 Commando and the 4-6 digit serial number. Pre-ban lowers are SN 35222 and below. All post ban lowers have the year appended to the serial number. Pre-ban lowers go for $400-$900 depending on condition.
Serial number list