SGW made the lowers for palmetto, and they were machined from billet. SGW is now known as Olympic Arms, and were the first commercial manufacturers of non-colt AR-15 type clones in the late 70's.
Palmetto had the lowers made by SGW under contract and finished/assembled the rifles with contract spares parts. Excellent quality on the lower, and with all colt parts used in the build, you've got a fine rifle there.
Only Palmettos I've seen in person were 16" shorty configs with telestocks and a 16" 1/12 lightweight barrel.