The SE1 was a simpler version of the SE2, without the exhaust throttle and whistle.
The boiler is 1 3/4" diam x 4 7/16" long. It has a 3/8" safety valve. The meths burner is the "vapourising" type. The feed pipe goes under the boiler in traditional Mamod fashion (to provide some superheating) and then directly to the cylinder. It has no in-line lubricator or reverser. There is a felt pad built into the port face for lubrication. The single acting oscillating cylinder is 5/16" diam x 3/4" stroke. The exhaust is fed, as usual, to the base of the chimney.
The paintwork is in reasonable condition and appears to be original.