Hi,
What are the dimensions, roughly? I used to work on bicycles a great deal, and this looks an awful lot like the friction lock used on a lot of narrow/racing bike seats...you know, so that they don't pivot front-to-rear. It's oily, but even the groove/rod space at the top looks to be the right size for the seat's underwire carriage.
Just my two cents.
Jack
WAIT: Just found a picture:
View attachment 21356
There you go.
It's not the exact same model, but you get the idea.