Hi, Dom. Many thanks for your reply.
As you can see in my photos, this particular flat base features a small plate for attaching support rods. It can be seen near the bottom right corner of the first photo. This appears to be a non-standard addition by a previous owner, probably with the assistance of a machine shop as you suggested.
The problem now is to find some support rods with the right kind of connector to dock with this plate. The mechanism, which can be seen in close-up in the last photo, involves two prongs and a hole in a straight line. I assume this would fit some kind of support rods that were popular at the time.
Can anybody identify the support rod connector shown in the last photo?
