Since the shirt advertises a defunct envelope company, it stood to reason this was an attempt at drawing equipment related to the business.
Carmen wrote from the U.K. with one possible answer, via her friend who owns a traditional letterpress printing shop:
“My initial thought is an envelope folding machine, they are usually long and low like that HOWEVER the big circle at the left looks more like a paper bag making machine. The circle might be a roll of paper (which is less likely for envelopes but usually for making paper bags off a giant kraft roll). The bit on the right could be for gumming envelopes.”
Carl, an amateur letterpress enthusiast himself, wrote from Michigan with another intriguing read on the illustration: “My theory is it is several presses and a type cabinet. First a Chandler & Price wheel operated press, then a Vandercook rolling press, and finally a type cabinet.”
He kindly provided visual aids for those of us who have never heard of any of those things. Thanks, Carl!