12 1/2 inches X 24 3/4 inches.  Well used, scrapes, chips on the wood, looks like soap in the soap saver.  I don't know about antiques but this appears to be unusual with a curved top.  You can see part of the word National and the cities of Chicago and Memphis.  I can't make out the other name.  The number 722 appears to be on the tin. You want old and used this is it.