The "Humbug" knife

[Mason]

We've all seen the Imperial "trick" knives which only open when held in one certain direction. They were originally called the "Automatic" knife in the 1930s and later re-named the "Mystery" knife in the mid 1940s. These models had two patents which oddly only referred to the handle construction and not the unique mechanism. The earlier patent was applied for in 1935 and the first known ad for these knives is in a 1936 "Hammer Brand" (Imperial) catalog.
With all this said, here is a catalog ad from 1934 for the "Humbug Knife" which is also a trick opening type model. Although it looks similar to the "Imperial" model, there are obvious differences like the handle pins and blade nail nick. Has anyone seen one of these "Humbug" knives who would know if it works as the Imperial "Mystery" knife did?

[dcgm4]

First time I've heard of that one. Very intriguing.

Hopefully someone has an example of one they can post here. I'd love to know more about it.