I've been looking this thing over. The plate is the same or a little larger than a quart paint top maybe in between a quart and a gallon. in the right picture with the carriage turned up there was a hole there. If you look at the bottom, left picture bottom right thats where the whole is. After looking at the edge it seems to be made to fit flush. So instead of a lid it might be a plate, and with the hole could be for a handle or knob. What ever it is I like it and somewhere there is an id for it.