This is a special limited edition of the Mamod SR1a Steam Roller, made to celebrate the 60th anniversary of the first version of the SR1 in 1961. This example is serial number 16 of 60.
Differences from the standard SR1a are: it has the long boiler as fitted on the TE1(a); it has a full length canopy as on the TE1(a); it has an extra large solid flywheel with a groove on it's outer edge as fitted on the Showman's engine; it has a brass plate marked "60th" attached to a pair of brass boiler bands and it has a special colour scheme with a red boiler and black wheels.
The burner is a standard tablet burner. On the standard SR1a, the burner handle forms a towing hook, as on most Mamod mobile engines, This edition comes with an optional plastic end for the handle, if preferred, as on most Mamod SP series engines. I assume it was intentionally included nd not a case of careless packing!
The boiler is longer than the one on the standard SR1a. The inside dimensions are, however, the same; the extra length being blanked off at the front end. (I'm assuming, here, that it is a standard TE1a boiler as it appears to be.) A standard 1/4" safety valve and a spring lever type whistle are also fitted. It has a water level sight "glass" (actually plastic) in the rear end. Boiler dimensions are 1 3/4" diameter x 6" overall length (approx 5" long internally).
The engine is a single acting oscillating cylinder, with a reversing lever that shifts the cylinder to line up with the appropriate holes in the port face. The cylinder is 5/16" bore x 3/4" stroke. The flywheel drives one of the rear wheels directly through a drive band located in a groove in the outer circumference of the wheel.
I have tested the engine in air and it works well. I haven't steamed it and probably never will.