I just broke the weapon down and found another stamp on the barrel but obscured by the stock. It's either 5P or SP, it's hard to tell at this point. Each of the three stamps is surrounded by an oval.
I don't know why, if these are date stamps, they would have 3 different stamps on one weapon. I still can't seem to find any definitive records on the stamps and codes used by Savage after they bought out the Stevens company.