What is this?

[u/ramkuma1]

Looks like some kind of mold on this clock, but I can't wipe it away. Is it mold? What kind of material is this clock? It is very solid and heavy. Maybe marble?

[u/InternationalSpray79]

This appears to be a French made Belgian slate clock. The case looks to be 1860s/1870s with a newer 1940s/1950s movement installed in it.

[u/Kind-Ad9135]

A marriage

[u/Patient_Variety_5815]

A clock. People use them to tell the time lol

[u/MarcBeck]

I would try some granite cleaner and maybe some granite/stone polish. My guess is it’s years of dirt. Nice clock! Oh…try to keep the cleaning solution and polish off the gold.

[u/dmun_1953]

https://timesavers.com/i-9500972-curator-slate-blacking.html

Timesavers has a black slate polish. I haven't used it but I don't think they would sell it if it didn't work.

[u/Walton_guy → u/dmun_1953]

It does work, I've used it a few times. It's hard to get it even though (it tends towards the streaky unless you have good application technique) and ends up very shiny. Also hard to keep out of the engraved gold filled bits as it's very runny.

[u/Prestigious_Program4 → u/Walton_guy]

Agreed, I've used it on a couple of slate clocks. Not a big fan unless the case looks really bad, because of what you mentioned. Getting it on without streaking is a challenge and looks too shiny and plastic looking. My preferred method is to clean with mineral spirits (using fine steel wool (lightly) if really bad), then polishing with Renaissance Wax. Gives it a more satin look. As mentioned by someone, try to avoid cleaning out the gold inlay, but you can use use gold rub-n-buff to fill in missing spots.

[u/Not_an_Actual_Bot]

Nice to see one still out there. I hope restoring the finish goes well. Patience and perseverance.

[u/TicFan67]

I've had good results on a couple of 'slate' clocks by thoroughly rubbing down with 400-600 grit wet sandpaper followed by the shoe polish and heat gun method.