If you haven't already seen this it's well worth reading. Most people haven't seen the M65A as it wasn't ever on general sale but a few have appeared on the secondhand market.
It's an odd looking hybrid of the M55 & M65, and quite unlike either. The M65A uses the M55 5-shot single stack magazine so this is the one you're after. You'll notice from yours that it's pressed steel and very strong.
The M65 is a longer & stronger action for .30/06 & magnum caridges (+ .308 too!). The M65 stock is broached for a broader magazine well, which is fitted with a 5-shot (or 4-shot magnum) staggered box magazine.
Apologies for the squashed up text. It's the encrypted browser I'm using - not me or the SD site