Tables were usually centered, but of unpredictable size, so putting it in the middle of the floor and running a wire under the carpet to the head of the table would be more practical.

Other floor buttons were in a spot where they could be stepped on easily.

http://www.colonialrevivalrestoration.com/Servants_in_the_Home.html 

It could be some type of switch controlling wiring for a receptacle somewhere, or maybe even had a wire coming out of the center that could be for a lamp on a table, etc. It's hard to tell from your photo, but the two holes on either side of the center hole could be on-off push buttons. It should be possible to better deduce the function if you took out the four screws so you could lift up the plate and look inside. Bear in mind that it could have live wires still connected, so exercise caution when poking around in there....

I had the exact same thing in a 1915 dining room. The very experienced hardwood refinisher who did the floor told me he'd seen many of these. They were indeed servant call buttons. Mine also was in the dead center of a long narrow dining room--if one sat on one of two long sides of the table easily reachable by foot.

The actual button had an extension cord, and this was its receptacle.

Casey

Of course--you are right Casey! For some reason I was imagining a foot contraption, but duh!

I never saw such a thing. How interesting. Thanks for posting this. I too thought it would be operated by a foot. lol

the place of honor in a table is the center, the heads are for less important people, look at any royal banquet and you will see the most important people facing each other in the center of the table, the button is there to indicate to the servants that the dish they served is finished and they have to bring the next, it is operated with the foot by the lady of the house, nobody should notice, it would be very rude and a sign of bad manners not having your hands visible all the time while seated at the table.

"the place of honor in a table is the center, "

Nonsense, unless you mean a dais for a banquet. Most of the stuff in the balance of your post is also incorrect. Not sure why you came back to this helpful thread with conflicting bogus info after more than two years!

i have the exact same thing in my dining room. Where could I find a replacement call button? Thank you for your help.

I have been searching and have never found a company which makes the anymore.

It may be out of a U.L. concern for fire exposure due to the direct current passing with a spark as you press down on the flower petal shaped top plate , contacting the round base plate on the bottom of what is an easily flat movable pedal . But I have experience with many great houses here in St. Louis with these and have never heard of such a problem. A metal worker could re-manufacture one if he had an old model to copy . ( then , to find a maid or butler to answer that bell ? Ha . They disappeared after WWI ).

I have the same one and it sits under the table and I could reach it with me foot and ring it but the button on it is missing and I’d like to restore it.