Some years back my Father had an Eastern Arms Co 16ga & I had a Central Arms Co 20ga. Both guns were made by Stevens & looked similar from the outside. They ad different internals though. The Eastern gun was a model 311 type while the Central was a 315 action type. The 311 type has internal hammers while the 315 was striker fired. They can be told apart from the outside by observing the location of the two cross pins through the rear of frame.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra