From Wiki - Made in Gainsborough Lincolnshire. A two stroke diesel.
The first single-cylinder Marshall tractor to be introduced was the Marshall 15/30 in 1930. It had a 8-inch (200 mm) bore with a 10-inch (250 mm) stroke (= 8.237 litres) and the maximum speed was 550 r.p.m., or 9.1666 revolutions per second. In 1932 the 15/30 was upgraded to become the Marshall 18/30. This model featured the same bore and stroke dimensions but the maximum r.p.m. was increased and the tractor's transmission was heavily modified.