The serial number letter identifiers, HM, on the J2L (square body) show that it was produced in June of 1969. This is a late J2 as they were discontinued by the end of 1969.
The system used for the J and J2 from 1940 thru 1953 would have been in the range of 200,000 to 299,999, affixed with a trailing letter to designate the production range to a specific month/year.
Starting in 1954 Maytag switched the system to start with a letter, indicating the production year, a six digit production number, and a trailing letter to indicate the production month. This was used thru 1959.
And in 1960, they switched the serial numbering system on the wringer to mimic the number system used on the Automatics, by using 5 numbers for the production sequence, followed by two letters to indicate the year and month. The year and month letter combos are universally used from 1954 through 1965 for the wringers, with the 06 series Automatics kicking off a universal set for 1966 forward, for all Newton made appliances.
At some point someone put an N2L (round body) model sticker on the washer, well after it left Plant 1 in Newton.
Ben