[Boatanchors] Question about Mic.

[Bob]

New Ham here, not young just new. 
I have an older conversion of a rack mount BC-625 transmitter that someone has done a lot of mods on but did a fairly nice job of converting. There is no power supply. It has been recapped but it hasn't seen any voltage in many years. There is an added 12SQ7 and I assume that rather than use a carbon mic, that it is set up for possibily a crystal mic.(just guessing on this) The mic socket is the Switchcraft No. 44. I would like to get this set running. Does any one have any suggestions as to what specs and /or what brand of mic might have been used on this? Does anyone have an older inexpensive mic that they are willing to part with that they think might fill the bill here?  Also there is a terminal on the power terminal strip that says it is for + 28 volts? It is connected to a transmit light on the front panel. My question is why 28 volts?   Any input for this novice will be appreciated.

73's

Bob Weaver

W1GTH