When was a Savage model 620 produced?

The Stevens M620 is an improved version of the M520 that was designed by John Browning. The redesign was to streamline the receiver. It was produced from 1927 until 1953. This gun was offered in 12,16 & 20 gauge with 26,28,30 & 32 inch barrels. It had a five shell magazine. It was never offered in 3". The gun was offered with a raised matted rib and was called the M621 with that option.

Your gun was not designed to shoot 3" shells. Source.... http://www.shotgunworld.com/bbs/viewtopic.php?p=830199&sid=568038cdcfc4d71ba0761dee536cdadc