I haven't come across this type of connection before. I purchased 2 antennas off of E-Bay and it came with this type of connection. I presume there would be a adapter so I can actually use it with my SDS-100.
There's also such thing as a Reverse Threaded TNC connection. Sometimes they are used and if you end up with one, don't take forever to see what the problem is, just get an appropriate adapter. Hopefully it isn't used on your connector.