After doing a bit of "Googling", I found the following for an Osco "Model M" overhead door opener. Look at page 7 & 8, part # 43, the motor, shows part number 2510-416.

https://www.nortekcontrol.com/pdf/osco/MManual.pd

Googling part number 2510-416, I found the following:

https://lineargateopeners.com/store/linear-part-number-2510-416-mtr-e-1-2-115-psc-m-jmb-hatch.html

Looks a bit pricey, but don't have anything else to compare it with.  It didn't list any specs, as far as dimensions, but it "looks" like yours.  Might be worth a phone call to them to talk about it.

Good Luck!