12,8cmx8,8cm.
The problem with these old ladies are the cracks.It is very difficult to find Monte Carlo plaques from the beginning of 20th century in good condition.
See the green square in the plaque:it was an area to glue everyday a different control stamp. This plaque had for the time a very high value- a real fortune.
How manny kings and dukes had this plaque in their hands??