What is it?

The Car Department needs YOUR help! The item pictured below was recently brought into the shop - the problem is, nobody knows what it is! It looks like a very short stool, about 6" high and 1' x 2' give or take, made of pine, with "CNSMRR 252" painted on it and a slot cut through the middle. North Shore 252 was a combine similar to our cars 251 and 253 but it's not obvious what purpose something like this would have served. Any ideas?