I think it's a Bang Mellow Yellow. If you look at the rear of the sole design it's more squared than a TaylorMade. Also, the loft designation is in exactly the same place and the Mellow Yellow is 420 cc's.
Sorry if this has been mentioned, but I didn't read all of the longer posts. But I had heard that the Lehmans have a thicker face. Have you measured this to see if it's true?