Unusual co-ax plug - what is it?

[ppppenguin]

I've found this unusual co-ax plug. Actually 2 of them with a short length of horrible looking cable between them. The outer is about 14mm diameter, the inner about 4mm. The whole plug is about 70mm long. No attempt at constant impedance design.

Any ideas what's it was used for? What it was called?

If you have a use for them then a small donation to Museum funds would be appreciated. Can bring to NVCF.