Burma Shave Rental Check and Letter

I thought some of the Burma Shave sign collectors might like to see these items I just acquired. The pictures might look a little fuzzy as I took their pics through a plastic sleeve and covered up the payee's last name. Both items are a little wrinkled but I am not ready to try to smooth them out.
Item one is an uncashed rental check from 1957 for the placement of 6 Burma Shave signs. The check is made out for $15 to cover one years rent. The next two photos are the top and bottom of an accompanying letter that requests the cooperation of the landowner in the upkeep of the signs and some terms of the lease. If you look closely at the U.S. map, there is a series of red dots along the roadways that represents every sign set in existence at the time I believe the letter is very rare and the check may be the only one in existence. I would appreciate any comments or questions.