Jim, don't know if you are still collecting MKII data but here goes. I came across a S&W .455 last week on GB and did an impulse bid as the gun which was going thru its 3rd or 4th time around without any bids. I bid the low minimum and it came in today. All I can say is WOW!!! BINGO!!! It is a keeper. I will post photos later this week on a separate thread. For your study it is serial number30783 and is marked .455. Hope this helps!