If it's a Mark III, is it stamped on the gun somewhere? Mine is marked as follows:
Browning Arms Company Morgan, Utah & Montreal P.Q.
Made in Belgium
On barrel visible from ejection port is: CAL 9m/mP
Below that appears to be the outline of a fish with some letters inside
First characters of Serial # is 72C
Probably made in 1972 but I don’t know for sure.
Paladin's right the firing pin safety is the main difference over the Mark II. I have the Argentine FM which is basically the old Mark I, which doesn't have the ambidextrous thumb safety, 3-dot sights, throated barrel and non-ramped barrel ramp of the Mark II/III. It does have the external extractor though not the weaker internal one of even earlier Hi Powers.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek
Mine doesn't have the ambidextrous safety, only the one on the left side of the slide. How can I tell if it's a Mark I, or II and what year it was created? It may be older than 1972. I've had it since 1987,