The first attachment shows the generators used on '51 and '52 GMCs, including your 1100013 number which was used on 100 thru 350 series trucks. "Tons" were only used by GMC on marketing documents, not in technical information like Shop Manuals or Master Parts Books.
The second attachment shows an example of of the marketing documents. I'm assuming that your "2 ton" is a model 350. So any of the generators listed for 350 models such as 1100013, 1105855, 1102716, 1100013, 1105003 or 1106757 could have come from the factory. And who knows what may have been swapped into the truck since 1951.
This
page from the 1953 edition of the GMC Master Parts Book should help you to figure out the "ambiguity" around 1951 vs. 1952. Just look at the last 4 or 5 digits of the truck's serial number as shown in the third attachment.
