What Duo is referring to as a end user is someone who is not a dealer or independent repair facility. Other words a company that actually uses the truck.
As he also mentioned for some one, even a dealer, to know the year of the truck with out a complete model and serial number is next to impossible.
The Clark "Clipper" was produced from 1941 through 1964 and went through many changes which would reflect in the actual model and serial number. So to get you the correct part they need the complete model and serial number as the parts would have changed through out the years of production.
If memory serves me right the 2111C is just the series and not the complete part number for the pump. From what I pulled up on line there are at least 12 versions of the 2111C pumps.
Your best bet is to take the pump to a local rebuilder and see if they can identify it. Or you can try Hader Industries they do a lot of rebuilding for the forklift industry. Their phone number is 877-388-2102
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