Jim Carter lists an SKF 18695 for 1933-1962 1/2 ton trucks.
The GMPartsWiki lists PN 592441 for 1946-1957 (that's as new as that particular catalog goes) 1/2 tons which crosses over to an SKF 18695
Rockauto lists different seals for various years, including the 5458 for 1955 and 1956, a NATIONAL 414045 for 1951 (which I bought and installedin my truck), 1952 and 1953, NATIONAL 450666 for 1954, NATIONAL 8362 for 1957, NATIONAL 5573 for 1958, no listing for 1959, NATIONAL 414045 (again) for 1960 thru 1962, NATIONAL 414045 for 1963 (1st design) and NATIONAL 8477S for 1963 (2nd design) and 1964
No idea why there are different listings, but your FLAPS may be using the same database.
You can probably tell from all this that I don't have much else to do right now.
