How would one polish/repair this ?

[Chopin]

As the title says how would you remove this "stain" or mark on the metal ?

Does this look like chrome/nickel ? Could this be plated or is it solid metal ? This is a Longines pocket watch from the 1910s in case anyone wonders.

I'm guessing someone may have tried some acid or stone testing on it to see if it's silver ?

I have some of that diamond paste that's supposedly used for mirror finishing but not sure how to proceed here.

upload gambar

Edited May 18, 2018 by Chopin

[wls1971]

Are there any markings on the inside of the case back if its European and silver from that era it will have some form of halllmark on it anyone testing for silver content and leaving a mark like that is an idiot imho.

I would guess at the case being one of the lower grade silvers 800 standard but this would be marked as such.

[Chopin]

It's not silver. I gave it a go with one of the polishing pastes that I had and it worked perfectly. Now pondering whether to "shine" the entire case...

I'm guessing it's stainless steel ?

[wls1971]

15 minutes ago, Chopin said:

I'm guessing it's stainless steel ?

Its probably nickel plated. Stainless didnt become popular in watch manufacture until the  early 1930's it was too difficult to work using method in use at the time and far too expensive a material when first introduced in 1913.

 

[Chopin]

Was the plating thicker than what gold plated watches are like ?

Because the case looks good and hasn't lost any "plating".

[wls1971]

I think the resistance to wear will have more to do with the hardness of nickle as opposed to the hardness of gold which is much softer, pocket watches on the whole fair better than wristwatches having spent most there life in a waist coat pocket.

But whatever the materials used if in regular use it will eventually wear but I have many plated pocket watches over 100 years old that are still in very good shape, but I avoid gold plated  or chrome plated wristwatches of any era because they dont hold up well to constant use once the edges of the plating on the case starts to go its all down hill from there.

[rodabod]

Be very careful with abrasives. Diamond paste can be aggressive.