What the heck is that key?

I remember seeing this a lot as a kid in the '60’s and 70’s, but I’d forgotten about it until this last weekend when I saw one in a hotel I stayed in.

I’m talking about table lamps that have a “key” in the side of the post. This key is NOT a switch. it has no function that I can see.
It can be unscrewed from the post, but I see no use for it. If it is mearly a decoration, why is it made to be screwed out? Like I said, it’s not a switch, and it’s not located anywhere near the switch. It’s on the post, half way up between the base and the bulb. None of the lamps in my house has this, or I’d scan a picture of it so you could see what the hell I’m talking about.

Any ideas on what these “keys” are?

Were the lamps made to look like the old style oil lanterns? They had a key on the side that one turned to control brightness by lengthening or shortening the wick. Maybe the designer was going for a nostalgia thing.