OffsetGuitars.com

I had good results using lighter fluid and Virtuoso Cleaner (very carefully!) removing this kind of "patina" of an old JM

Yup, naphtha (lighter fluid) is great for cleaning.

I've had good results with 151 rum (but not on french-polish), definitely a multi-purpose cleaner. The dirtiest piece of equipment I've ever handled was an old Shure PA mixer that came out of a strip-club, it was like it had soaked in a vat of nicotine for 30 years, the chassis cleaned up ok but I swear the reek had soaked into the knobs and I ended up replacing them.

Honest wear-n-tear is one thing but human origin special-sauce really holds no mojo.

What's up with the route peeking out from under the pickguard behind the bridge? Weird. Anyway, clean the hell out of it. I second what's already been said here. Dirt and grime is just that, and you don't want someone else's whatever getting all over you. Plus it should play and feel much better after a good cleaning, and that's what we all love about old guitars the most, right? How superior they are to the new ones, so be sure you're getting the most out of the instrument.

You should have saved the dirty grime thingy, stored in a small can for just in case you need to reverse the modification.

Looking really good.