Can someone identify this connector?

I grabbed this SMA bullet for some measurements, and after the vswr was bad I noticed that this bullet has SMA threads on the right, but the left has some sort of weird thread that I am not used to. It will thread onto an SMA male, but does not appear to seat fullly. What type of connector is that on the left side? Thanks!

It looks like an adapter rather than a thru.It might be 2.92mm-3.5mm adapter or 2.92mm thru..

I thought K and 2.92 mm connectors had only air dielectric, and the left side connector has teflon dielectric.

The SMA vendor always manufacture various connector according to our request.
Let me guess:
1. it's just a adapter between SMA and 2.92mm
2. It's a isolator, because the middle of it have some black points.
Can you test it?

It is a transmission line bullet. A simple passive thru. The little black dot is epoxy that is used to hold the center conductor.