I found an adapter in my junk box that goes from a BNC to something similar
to a male N type. It will not mate up to a female N connector.

A normal N male connector has the center that is just about even with the
shell that screws onto the female end. This connector has the male part
sticking out about 1/4 of an inch past the shell. It will fit the female N
connector except when I go to screw them together, there is not enough
threads to mate and make a good mechanical connection.

Anyone know what type of connector this is ?