On Tecumseh-engine motors produced by Eska under a zillion different brands (not Mono though), I’ve been able to determine the year and HP a couple times by looking for a small metal Tecumseh (TEC) ID tag under one of the carb screws. That tag can sometimes be cross-referenced to a Tecumseh carb rebuild kit chart that gives year and HP. Attached is a table for Tecumseh-produced Eskas for Sears Often that tag gets tossed out during a carb rebuild. You may find the carb number at the chart in the link below, and the HP and year should be close to that given for a Sears-Eska that uses the same carb. :
Dave
https://discount-marine-parts.com/ob_eska_sears.html
.
.