Vintage RCA Varacoustic microphone mic

Hello, I can not find a model # on this RCA microphone and I'm assuming it is a Varacoustic type. It does not have a plug on the end of the very long cable. Using a AA battery and the ends of the mic wires I could hear the diaphram is working. I may try and wire a 1/4" jack to it to better test before the end of the auction.