This month's mystery engine comes, as usual, courtesy of John Spalding, 112 Carriage Place, Hendersonville, TN 37035 (firstname.lastname@example.org). Judging by the photograph, these boys had been working pretty hard when they stopped for the photographer.
There's no information on the photograph telling when or where the picture was taken, or what the engine is, but we're sure an eagle-eyed steam fan will be able to figure this one out.
As ever, the first person to correctly identify the picture, by mail, gets a free copy of Professor P.F. Rose's Steam Engine Guide. Good hunting, and get those answers in quick.