1937 Velocette Mac 350cc

The Velocette MAC is a British motorcycle made by Velocette. A reliable single-cylinder, the MAC coped well with the low-grade post war petrol and was a popular commuter and touring motorcycle. Although they started as innovators, Velocette failed to keep pace with developing technology and production ended in 1959.

https://en.wikipedia.org/wiki/Velocette_MAC

As Found

The MAC was born in 1933, the first version having an engine with a displacement of
350cc and a top speed of 75mph.

The core engine was acquired in the UK. The parts needed to make it a complete engine came from Australia, Canada, the UK, and the USA. Other miscellaneous parts were sourced in countries not mentioned above.