Engine number R136726 stamped into the casting on the side of the seat tube/ top tube

Hi folks, this is my first post since I don't actually have an Ariel. I have a T140 and an RE 350cc but have recently purchased a mystery frame that is some kind if Ariel 250cc. Can anyone shed some light on it please? It's 1931. Cheers, Olly http://i978.photobucket.com/albums/ae267/brotherfergus/P1...