I tend to think Uniglide as well. The dust cover over what is almost certainly the outer bearing in the freehub body is the clue. A freewheel simply does not use a cover of that sort.

If we're right and this is a Uniglide then there's nothing to be gained by removing the cluster. Use regular and cone wrenches to remove the nut, spacer and cone from the non drive side and slip the axle out, Clean and service as normal and re-assemble.

The good news is that the old Uniglide cogs are tough. I used one for years on a single speed. The bad news is that if and when they do finally wear out that you'll have to toss the whole wheel unless you hunt down a NOS Uniglide cassete.