Age for Singer Thru the Wall unit

Looking for the age of a Singer thru-the-wall unit. Ser#404480171
Model# 2EA15B3C. May be 1970’s vintage. Thanks.

I’m no help whatsoever on that unit. I look forward to help from some others so that I can add to my research.

old post regarding singer

http://www.nachi.org/forum/archive/index.php/t-1076.html