Tom,thank you for your informative response. I might have stumbled upon the holy grail. I will post pics if a multi gauge LC Smith I have acquired. Dr. Jim sent me a research letter on the gun and it may be a one of a kind Smith having both 16 &. 20 gauge barrels. Both sets are numbered to the gun and the research letter states the gun went back to the factory in 1940, probably to have the 20 ga tubes fitted to the gun. The fit on both sets of barrels in fantastic ! More to come