Very '50's -
⇧ looks like it's one of my favorite collars: a rounded-end collar (club?) with eyelets cut in so that a "bar" can pass through and be secured with "screwed ends" to work like collar bar, but much more secure.
I have both the cube and ball kind, sitting unused like most of my wonderful classic attire and accouterments. But it is one of my favorite "nuanced" item from the era. Thankfully, I don't remember ever seeing one with gems.Absolutely! I was wearing collars like this in the early '60's (Which incidentally have nothing to do with The '60's.) The most common ends for the screw on bars were ball, or a cube. Though I always thought the cube coolest. (Uncool guys had gems in theirs. )
An interesting illustration with more than just a bit of mystery built into it He is impeccably dressed, so much so that he has secured the undivided attention of the cute and perky girl next door, but what is that contraption his left hand is glomed onto? Some sort of signaling device, perhaps? .