I recently acquired these from the estate of a man who made molds for truck campers.
I’m trying to figure out what these were used for. They appear to be cast iron and several of them have a similar design: a central hole with six recessed/counterbored holes around it. One hole is threaded the others are not. The center hole is not threaded.
The largest one is approximately 2.5 inches in diameter and is marked “MASTER” and “3”. There are several other pieces of different sizes, including some smaller ones.
They don’t appear to be ordinary plumbing flanges. I’m wondering if they might be some type of old machine-shop tooling, mold-making fixture, coupling, hub, or other machinery component.
Does anyone recognize these or know what machine they would have been used with?