At the time of writing in 1933 he was over 70 yrs. old. .... and his grandmother was born in 1800 - so I would put the date of the exploits of the Cherbourg at the end of the 18th. and the beginning of the 19th. century. I can't get closer than that .. but would be pleased to hear from anyone who can.
The fast revenue cutters that chased the Cherbourg were designed for speed, and in fact were contributary to the virtual stamping out of smuggling towards the middle of the 19th. century.
A little ship that could outrun them was rare indeed.
This was a common title in Cornwall - then the source of the best hard rock miners in the world.