I picked up this lovely Kiwi Florin from a member here for a fair price, three of them actually. It is 50% silver and I thought, looking at them, that they had surface dirt on them I soaked them in acetone for about 48 hours and then rinsed them with some imporvement. I was wondering how I might further, safelty, tream them.
I don't have any practical advice, but I will say I have experienced similar spottiness/streakiness with .500 silver coins sometimes. I don't know if tinkering with that one would be worthwhile, given the downside risk, and the fact that it's not awful as-is. A little streaky? Sure, but tolerable, I guess.
I like those, nice size and the kiwi bird is funny. Please post more pictures if you take further steps, I'm always curious about conservation issues.
You could dip the coin but I don't feel it's a good choice for that. It has the look of an improper dip, long ago. The obverse looks like there is some luster under the toning. A dip would remove some or all the toning but may harm any luster that is there. The coin could turn out really ugly. Once all the toning is removed, every little tiny hit/contact mark is going to stand out and smile for the camera. Not a good look. You can have this same problem with just an acetone bath. Junk on the coin can be hiding tiny marks and scratches. There are always risk when you mess with this type of stuff.
I am not trying to kill the surface or effect the toning. It sems to be physical dirt or grease on the surface, or so I think.
Your coin is corroded. That may me why the price was so good. I suggest you do what the seller did. PS Acetone is for certain substances, otherwise it is totally useless.
It looked better when it was wet, but as it was then soaked in distilled water and then dried, the stains seemed to reform on the coin surface. I was tempted to use dishwashing soap and water.
I guess I was too vague. Acetone, soap, and water will not give you the results you wish. What may happen is you will damage the coin when playing with it using the wrong products. I suggest you either leave it as is or sell it. If you must, you can search the Internet for coin cleaning tips or send it off for conservation which I do not recommend.
It sort of depends on what you want to do with the coins. If you plan to keep them but enjoy a bright coin, a quick dip should work. If you plan to sell them down the road, leave them alone. Acetone and rinses should have removed all you can without any damage to the coins.