I found a little info on the company. Of course you can't trust everything you read, but seeing as it was hard for me to find ANY info, I guess it's better than nothing.
http://www.rockisland.com/~tonewoods/fentone.html
Apparently it's a Japanese company that made a number of mics. This page features a different, probably more recent one.
Here's a pic of another Fen-tone mic:
http://users.belgacom.net/gc391665/fentone.htm
I found this about the Fen-tone "crystal mic:"
"Fentone crystal mic. This "Made In Japan" high impedance mic looks like a miniature RCA 77, and is really good at sounding really bad. Run through a tube direct box, it gives the best (and cheapest) vintage sound I've ever heard - no lows, no highs, instant 78 r.p.m!"
And another:
"I have a Fen-tone mic thats quite glorious in a completely awful sort of way (or is that quite awful in an glorious sort of way? Oh well, no matter). It looks kind of like a little blow drier. I use it quite often for that trashy vocals through a guitar amp thing. Mines not from the 60's though, its fairly recent. I know Fentone made some older mics that were crystal mics in plastic shells that looked kind of like RCA77DX's (and I'm sure they were every bit as
good, too <g>) Pretty junky stuff, but everyone's got their own idea of "good junk". I consider my Fen-tone mic to be 20 pretty well spent dollars"
So maybe it's worth playing around with, especially if you're looking to get a sort of dirty somewhat vintage sound.