Yes. .. 1925 + 51 = 1976 expiration.

It is a common belief (although debated) that the regulations set a 3 year expiration so the actual year of manufacture is 3 years prior to the expiration date. Thus your machines month / year of manufacture is September 1973 (if we follow the 3 year expiration rule).

Cool machine for that early to have electronic solinoids.