Hello all, I recently picked up an older Savage/Stevens 311 series H side by side for $250. I'm looking for perhaps a date of when it was made and how can you tell what choke the barrels are?

The serial number is B722307 and it has 28'' barrels.

Also, when I was firing it the other day it was shooting well until both barrels fired So perhaps something is worn and needs to be replaced?

Thanks in advance for any replies or information that can be provided