I bought a preban rifle today off of an older gentleman. I had some questions to which I have found some answers by using the search function.
I know now that all or most EA recievers were sold as stripped lowers. So obviously this is a kit rifle. It had a A1 style barrel with A2 handguards on it. The reason I know it is an A1 barrel is because the handguard retainer behind the front sight is triangular. The barrel is marked FNMI MP CHROME BORE. The upper reciever is marked PM below the rear sight.It is also A1 style. My question is this. What does the PM marked below the rear sight mean? It is also marked 3 R W on the front sight. I found a link to biggerhammer's upper faq but it didn't have PM listed. It's stamped just as colt stamps theirs except instead of CM it's PM.
If anyone knows anything about this please shed some light on this. Thanks in advance.
I'm planning on finding some nice A1 guards to put on this rifle.

Essential Arms never sold complete rifles.  They sold lower receivers, and matching A1 and later, A2 upper receivers.

A sister company, Essential Accessories sold kits MINUS barrels.  They did not stock barrels, and would recommend several suppliers.

They also manufactured and supplied to the industry aluminum CAR stocks.

All rifle length barrels have triangular handguard caps whether A1 or A2,  Carbines have round handguard caps.