It's almost completely unrelated to anything I've done so far, save for the fact that it runs in MESS: It's the Manchester Small Scale Experimental Machine, or "Baby", purportedly the first stored-program digital computer!
This marks the oldest system, I believe, to ever be added to MESS, with a year of 1948.
A pretty screenshot is located here:
http://moogle-tech.com/blog/?p=118