The knife in the advertisement is not a photograph of a "prototype", it is a drawing, a graphic artist's rendition of the knife. A sample of the knife may have been sent to Norm Thompson for changes and for approval, but unless you have a knife with provinance (a tag from the maker, a photo of the exact knife sent, a knife with coded sample markings etched on the blade, letter from the maker or original owner), you most likely have a knife from the special factory order production for Norm Thompson which he sold through those magazine ads.
It is a common mistake to call a sample a prototype. Most SFOs did not require a prototype since they were based upon previous production patterns. Altered production pieces with added features requested would be sent to a customer , then usually returned to the factory as a "go-by" for the production pieces. At this time, it is unknown just how many were produced for that customer. It could well be one of a gross (dozen-dozen = 144) or more likely one of one thousand or more.
N.T. bought several patterns from Schrade Walden for special promotions, both fixed blades and folders. Yours dates probably to 1964-65. We have researched a fixed blade knife, the 165OT "SHIKARI" which dates to 1966-67. They were serialized, but we still don't know the exact quantity produced or the exact time length of production.
