Button Identification?

I recently moved into a ~1900 rowhouse and found this oversized “button” near our old dumb waiter shaft. It extends through the wall to the other side. A friend who lives in a similar building has the same button, but it is not near any (extant) dumb waiter.

Can someone help us to identify this? Is it a call button for the dumb waiter, or for a servant? It’s been painted over so many times at this point, it’s hard to identify. Originally I thought it was an old, sawed off post!

By slopette |