With no stamping details on the blade, handle, etc., it sort of screams improvised, knock-off or clone, if nothing else. May not be a Camillus at all. Carbon steel blades with a stainless handle seems oddly mismatched as well; makes one wonder what the intended market was for it, if it was by design. Sounds more like a knife thrown together from a mix of parts, maybe a 'lunch box knife' put together from new parts by a factory employee.
I did come across another old sale listing (expired) on the web, with one each of two old Camillus patterns made for Sears/Roebuck in the 1920-1940 time frame, side by side; one is the old Camp/utility pattern, and the other an equal-end Cattle pattern (stockman), both of which the vendor specifically states are apparently built to the same pattern/frame (3-3/4" closed). Identical size & shape. So, if someone at Camillus had access to unstamped parts for the patterns, including access to the MIL-spec stainless handle version of the camp knife, maybe it could happen. But, who knows...
Without a link to the pics at least, we'll probably never know. Or, even with pics of an unstamped knife, for that matter.
David