Nice hunt today but need help. Found a 1916 Mercury dime. d?

[Johncoho]

I am only posting the 1916 Merc dime as we have all seen clad and some of the other relics I dug today. The dime is far from mint condition, and would have to rank poor as you can see. I also found some foreign coin that needs electrolosys. Spelling may be wrong, but what I need is advice on how to clean the heavy layer of crud off the back of the dime so I can see the mint mark if it has one. I have tried the aluminum foil, hot water, and baking soda on some other silver that I have dug here with limited success. The obverse of the coin was mostly just dirty with some minor crud, and cleaned somewhat under water. When I saw the 1916, I stopped the cleaning process. The ground is extremely hard on silver where we are in Arizona. The last coin I did with the aluminum foil and baking soda took more times in the baking soda than I can count and it just couldn't cut the crust on the silver. I have heard of soaking coppers then freezing them to break the crust off, but would it work with silver. I know the coin is pretty crappy but it would make my day to know if I have dug a 1916d. Any help would be appreciated. I have cleaned the 1916 Merc, and the only D I see is right before the ime. Thank you.

 

[Professor of Engineering]

Congratualtions on the 1916 Mercury dime, I sure hope it turns out to be the D mint variety!