SD - Thanks for that and yes it looks something like that but I suspect it's a lot older. The gearbox on mine is a square block without any of the profiled indentations. It also doesn't have a winch handle socket on top, there is a large screw that appears to hold - well - nothing.
The parts that are displayed on your link are similar but not the same. I found a PDF on the Lewmar site that sort of resembels my unit but the exploded view doesn't really show how it comes apart and that's what I don't know.
Here's what the thing looks like:
The top knurled bit screws off and both the drums can be removed without removing the screw on the top. This is what it looks like with the drums removed.
The cone on the bottom forms a friction joint with the chain gypsy but this is the part that I can't seem to move off the shaft and it clearly prevents the shaft from going into the boat. But it has no visible retaining device (keyway, circlip, etc.) and it turns with the shaft.
These are the two drums and where they interface (the rope drum is upside down). The rope drum and the chain gypsy have a friction cone between them as can be seen with little cut-outs but these have no obvious purpose other than perhaps carrying grease.
This is the bottom of the chain gypsy where it interfaces with the cone on the bottom of the shaft.
And after all that, my mission is to get the shaft to either come off the top with the friction cone or the friction cone to come off the shaft. I just can't figure out how
Hopefully there's a forumite around who works with these things that can help.
Thanks so far.