piezo electric co LTD piezo HM-7 crystal mic

Hello,

My name is ben and i have just recently bought a microphone
from ebay just because it caught my eye and i thought why not.

I have been looking for information about it but cant seem to find anything that is of relevance!
If there is anybody out there on the internets that can help me with a time period and compnay that would be awsome,

Thanks anyways