hi kayakersteve, it's a stainless file guide with a carbide face like the ones Bruce Bump selles, it's an amazing tool for plunge lines and shoulders for hiden tangs and even setting bolsters.
it's a method i learnd from a jeweler friend of mine, the foundry i work with can cast brass and any kind of gold as well,
it's not pictured but before i send it to the foundry i attach a small wax rod by melting it onto one of the flat areas, jewelers call it an "ungus" and it serves as a entrance for the silver to pour into and a mean of attching the wax model to the casting "tree", it's sended off once the model is cast, it's important to make the wax model a bit larger then the actual size you need as the surface usually have imperfections that need to be sended off.
i'll start with saying that i never thought i would ever do a knife with stone setting in it, it's just not my thing, but i do like to take the occasional design challenge by steping out of my comfort zone, this was definitely one of those occasions,
the bolster was sent to a stone setter named oleg leybman how did an amzing job, the stones are black zirconia
here are some pics:
PS i still don't have the bolster myself and only saw it in pics, hopefully tomorrow it will be here.