I seem to be on a bit of a roll with picking up interesting old Peterson pipes at the moment. The latest addition to the herd is certainly one of the most interesting that I have ever acquired.
When this pipe first appeared on Ebay there were no clues in the item title or description to indicate its age or type. The one photograph in the listing made it clear that it was a deluxe of some sort and the shape immediately said "3s" to me, or possibly "2s". It's hard to judge size in a photograph without a point of reference.
However, the pipe turned out to be much smaller than a 3s, let alone a 2s and it has the magic words "Peterson Patent" stamped on the shank and band. Checking the 1896 catalogue it looks like a 21½s. The hallmark is K for 1905, so this is now my oldest Pete. It's just 115mm long, the bowl is 35mm high with an bore of 17mm. It will be perfect for ropes and twists. Once I've cleaned it up I'll get some decent pictures taken, but for now here's the "before" picture.
This page from the above mentioned catalogue shows the 21½s models with the different stems available then.