Arrived home this afternoon and, as promised, here are images that I hope will explain what I was writing about with regard to the tenon of the 1910 Barling being stuck in the mortise.
Here's the picture of the pipe in question:
You can clearly see a circular object centered in the shank. The amber stem has a threaded connector extending from it. Were the tenon not stuck in the shank, the stem assembly would look like this:
Barling used a threaded connector to attach a vulcanite tenon to the amber stem. When I originally bought this pipe, the tenon was stuck in the mortise and I released it, cleaned it and the mortise, and screwed the tenon back onto the threaded connector. I would have unscrewed it to take another picture, but it didn't want to budge and I'm not going to force it. It seems to be happy to be back in place.
The reason for this construction was to provide a stronger and more durable join than either using an amber tenon or a bone tenon, both of which are fragile. Barling was pretty early in using this solution at a time when other makers were still using bone screw connectors. Vulcanite has more tensile strength than amber, which is brittle. This pipe dates to 1912. Here's a picture of the pipe:
It's a nice looking pipe with very fine straight grain going 360˚ around the bowl.
Besides, who in their right mind would deliberately cut a bone connector, as the sole connector, that looked like the one showing on the 1910 pipe? All those threads? You would be turning and turning and turning the stem many many times to get it seated. That's a lot of stress to apply repeatedly to a fragile connector.
So what would an actual bone connector have looked like? Well here's an earlier Barling from 1896, coincidentally also made for JB, and it has a bone connector that is quite similar to many others that I've seen.
Here are a couple pictures of the pipe:
And here's the pipe with the stem removed so that you can see the bone connector. It's threaded only at the base, where it also widens out to be a bit thicker and stronger. The tapering makes it easy to insert into the mortise. A few turns and it's seated.
I hope that this helps clarify things.