Well, I improved it a bit with a cotton bud soaked in lighter fuel (which made the rust spots smaller). I suspect a previous owner wasn't so careful while cleaning as a load of scratches appeared under the muck. It's usable but really just gives you a vague idea of what you're pointing at - not quite as good as the WLF or prism finders on my Bronicas!

I'll have to try the nail varnish, I wasn't really planning to tidy the paintwork up but if it's that simple...