That's not a date code, it's just a proof number or inspectors stamp.

Found a bit more on the 5000's, I guess the 5000 was made from 1921 to 1931 and then changed the name over to the 5100. I never even heard of a 5000 before this so I'll have to keep my eyes open for one.

If I were you and wanted some cool info on it I'd write a letter to the Savage historian and get it lettered. It's your grandfathers gun so lettering it would make it even neater to see where it went to when it left the factory and what year it was made.