Hi all,
Looking to date a unit I’ve never heard of. Electric Products Mfg. Corp. based in Mesquite TX.
The house was built in 1975 and it looks to be that old, but maybe not.
Serial is: E41-128592
I’m thinking it was built in the year of our Lord 128,592. About the 41st day of the month “E”.
We just ran across the same manufacturer for the fist time, unable to divine anything from internet research did you ever figure this out?
Wow, my memory was never good, but 2009? Nah.
I think I just put it down as an unknown. 
Good Luck
Guess I didn’t see the date of your original post. I did find some answers for the future. EMPCO began manufacturing units in 1964 and was bought by Comfort Control Systems in 1975, a Square D Company. Then Square D sold the division to Sun Dial which stopped manufacturing the units in the 1980’s. So we will probably not run into many of these old units.
The information came from a merger and acquisitions pdf I found online. For what it s worth and anybody else that happens to search out this discussion
I started to say that I had found it was the old square d company. but I just couldn’t remember for sure… so that’s what I told you I got a bad memory