Eastern Arms 101.7, 5100

I'm looking at a 16 ga. Eastern Arms 101.7 sxs, 28" barrels. It has Eastern Arms 101.7 on the left side of the frame and 5100 stamped on the right side of the frame. Seller wants $300. Frame still shows good case color and bluing on the barrels is at least 80%. Action is tight and bores are perfect. Can anyone tell me when it might have been made? Is $300 a reasonable price?

Also, what is the difference between this Eastern Arms 101.7 (5100) and a SXS marked Springfield -J Stevens Arms, Chicopee Falls on the left side of the frame and Eastern Arms 101.7 on the left side of the frame?