Hello
Dince and
Mod Alan MI have always found these odd but interesting machines.
There seems to be little information 'out there' on them.
The
VHGMC is probably the best starting point: -
http://www.vhgmc.co.uk/photo-galleries/atco/Both the Atco Boat Propellor and the Atco Scythe appear to be
post-WWII designs, selling here from the late 1940s.
[Sir Chook has discovered the Atco is an inter-war design (below)]Please let us know how you go with this one.
All the best-----------------------------
Jack