well Yale produced the Eaton/Yale brand lifts between the years 1963 and 1971. I know its a broad time span but i hope this gives you and idea of the generation when it was mfg'd.
on alot of those older lifts the serial numbers were stamped in the rightside frame on the side of the truck just about where the footstep/entry area to the operators compartment was. (you may have to scrape paint and clean it off to see it)
Also may be on the fender on right side (if it has one)
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.