VCCA Home Forums TECHNICAL - GENERAL Radios, Tools, Accessories need info for a 35/36 locking gas cap

been wondering on how far back the 1940s GM locking cap goes back to
can anyone shed more light on the earlier ones?or were these all the same?
pictures would be a big help
looking for 35-36 style locking gas cap

According to the parts book the 1936-1941 are the same.
The picture in the 1934 accy. book makes the 1934 look like a 1936 but isn't listed as fitting any newer than a 1934.

this is the cap that im talking about
guys have these listed as "earlier"

Shown in the 35 accessory book. There were also universal ones sold by the same Chicago manufacturer. The photo is correct and has the defined rib. The generic has a smooth rounded rib.