It's nothing unusual, just an older 3/4HP engine, these Type 133 engines have turned up with a wide range of serial numbers indicating the military were wasting tax payers money for several years and leaving us with plenty of nice NOS engines on the surplus market too.
David
P.S. What's the Somme (WWI) got to do with it? We don't want that getting out, as it's bad enough people incorrectly listing them as WWII vintage.