:) Hi Michael! That type of connector is called an amphenol type 2 conductor. It has been used on coax cable on everything from CB radio mics, antennas, small house PA systems like early Bogan products used for industrial systems, also in early TV broadcast equipment for video coax, home type tape recorders. It predates other connectors like the BNC, and XLR for common use. It provided a secure connection because most of the early mics were high Z, although some had lower impedance's at about 1 to 2k, providing a little extra cable run. The transformer is actually inside the mic rather than at the head of the pre.

Very good cable was needed for any serious runs, and even then there was considerable roll off in the highs. Unless you plan on just collecting this mic, for runs longer than 10' to 15', you may want to modify the mic by by-passing the internal transformer, and fitting an XLR pigtail at the mic end, with pins 2 and 3 to + and - respectively on the diagram, and 1 to case ground. I remember our first bands could only afford a Bogan PA amp, and all our mics had those connectors, EV's, early Shures and many other brands. There was always some noise getting in on the stage from something.

--Rick