Hmm. I actually have a vague recollection of that mic from way back when, but only very vague- I think one of my old collaborators had one... A quick Web search indicates that it is moderately popular among the concert bootleggers as an easily-concealed recording mic, and that it currently sells for around $50.
Is it a stereo mic, by any chance? Since the bootleggers list it as a common mic in that use, I would suspect so. And that might explain the odd connector as well (2-channel single-ended output, as opposed to one balanced mono output). If it is stereo, it's probably a mid-side design. And as such it'd probably be interesting for overheads, room ambience, and so on. If the bootleggers like it for making their illegal tapes of live shows, it might not sound like complete trash (although the caveat about high-SPL distortion still applies, with that 1.5v supply).
The problem is that Sony has used the "220" model number too many times on their mics- there's the old C-220, which is an '60s tube muc, their current FV-220, which is a low-end dynamic... The ECM-220 is definitely an older, out-of-production mic, and I don't see it listed on the equipment lists of any current studios (although a concert hall in Australia lists two of them on their gear list), but that doesn't mean a dadgum thing.
Come to think of it: if it is a M/S stereo mic with two single-ended outputs, you could probably get a *very* odd sound out of it by running one to pin 2 and one to pin 3 of a normal balanced input... It might not be a _useful_ sound, but it'd be unusual, for sure. You might actually like it, especially if the vocalist moves around a lot as he sings. This would be an amusing workout for the mic preamp, too, because the vast majority of the signal would be common-mode. Different preamps will do different things with this: a low-end transformerless preamp will give you a radically different sound than a transformer input stage.
Let your ears be the judge. Hang it, experiment, see how it sounds, and have fun! Some of the best special-purpose mics I had for my old studio came from pawnshops, bought on a lark, and I'm still kicking myself for having sold them...