I Really Need Help Understanding What's Wrong

I don't know what these coins are made out of, but I believe that water is only meant to remove organic material. Use 100% pure acetone or some Verdi-Care to get rid of the verdigris (green stuff). Never use steel wool unless you're positive there is no other way.

One step stronger than distilled water is pure olive oil... this is very mildly acidic but I am not sure it will help in this particular case as it is better for stubborn deposits but not really strong enough for hard mineral deposits, it still requires time and keeping a good eye on it.

Steel wool is out of the question but picking with a cocktail stick is sometimes viable.

I gave cleaning a short attempt but I haven't the patience and the quality of the coins was unsatisfactory to me... good luck though I wish you every success.

Thanks everyone.

@RoyCoinBoy: yes, no steel wool at all, bad idea even for the second coin. I will mechanically work on this one under the microscope, using a small chiesel and a dental instrument.

@DavidUK: true, cleaning ancient coins is more an adventure, another side of numismatic, where lot of patience (and knowledge) is involved. I do have more of the first one.
@Moxking: the first coin will enjoy a long bath in olive oil.

However, I found these 2 videos, where the uploader took an archeologist way to protect ancient coin. A process with lot of care, even for an unrecognizable coin. Part 1: https://www.youtube.com/watch?v=53q8cxaMuvE
The uploader also suggested a couple of books in the videos.

The benzotriazole is not something that I would use in my apartment, but the chemical reaction seems to be helpful in treating the bronze disease, more than sesquicarbonate.

Did anyone tried this chemical solution for bronze coins? Just interested in knowing if Verdi-Care can be a better idea.