Well I bought my American Yanmar from a good ol American Farmer. A Firefighter, even. Look what I found:
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It took everything short of a slide hammer to get that filter out. The coil spring jumped at me when I took the cover off, showing that whoever went in there before had botched the tabs then clearly didn't replace the filter.
When I got the replacement filter and o-ring, I noted the o-ring I had found in there was far too fat. The bogus o-ring had crushed the filter's shoulder, and then cooked, to become a severely strong adhesive.
Amazingly the hydraulic system worked fine before and after I replaced the filter, o-ring, and fluid. (I also flushed the transmission case with diesel). The filter looked intact when I first looked in there and saw its inner surface, but it had to have been neglected for a couple of decades.
Buyer beware - check everything if you didn't buy from a first-class dealer!