Another daft idea, but could it be a heavy duty sewing machine, for edging canvas or leather?
There is a gap marked in red where cloth could pass underneath as in a sewing machine. Possibly the pulley feeds thread (something hefty like sisal, not cotton.)

The two wheels just grip the material and pull it through the head. One side is plain to minimise damaging the material, but whatever it is, it's tough heavy stuff.
Alternatively it's a punch or pricker, used to make eyelet holes along the edge of leather, or thick canvas sheet for big tents, sails or large tarpaulins.
The small pulley supports the edge as it passes through. Maybe there is a twin on the other side, and perhaps they were connected by a belt to improve support, but it's just a roller. Mode of operation:

- The gap between gripping wheels and the head is set to suit the material with adjuster A
- The punch depth is set by adjuster B
- Turning Crank-handle C pulls the material through the head and under the punch as far as wanted
- Holes are punched by pulling handle D.
Used in a factory rather than by an individual skilled sailmaker doing repairs or making small items.
Dave
PS One of my uncles trained briefly as a sailmaker after joining the Navy during WW2. I was surprised, but he explained warships require hundreds of bespoke canvas covers to protect guns, aerials, and anything else delicate and exposed to the weather. Highly skilled work. Didn't last – he spent most of the war in Canada as a trainee pilot. Wish I'd asked – from what little he said almost certainly Coastal Command Liberators.
Edited By SillyOldDuffer on 27/04/2021 15:08:41