There should be information in the lower left or right bottom of the glass. Should give you the maker of window. Is it a replacement Unit?
http://diy.stackexchange.com/questions/14466/how-can-i-identify-the-manufacturer-of-my-windows
Thanks for sharing. I could never understand why people do what you do but I do admire you for doing what you do. good luck with all the hard work that you are doing.