I am less expert at the topic than you might think !
My brother (MARCVS OBLIVIVS) is my go to guy for BD. I went looking for pics of my Caracalla to show the results of his treatment. The coin after a year in 'storage' showed obvious signs of fuzzy green nodules forming in association with orange encrustations which clung tenaciously to the coin.
Being one of my favorite sestertii I immediately handed it over for the 'cure' !
The previously mentioned orange stuff had been cited by several experts as a removable blemish. Fearing for the worst I had hesitated (unless you know for sure ........ Always hesitate !) to do anything.
The 'cure' stripped away much of the dark patina and left the coin looking less than it had been but I believe the good Doctor in this case had opted for a more radical regime of baths.
The fear often is that once the BD penetrates into a coin the cancer may spread unobserved below the surface. Once you reach a certain point (stage 4 !) the surfaces will simply crumble if treatment is made.
I have an earlier pic which shows the nodules in the early stages. As the green specs did not appear to be soft I hesitated to do anything irreversible. Once the growth became obvious we erred on the side of caution and extirpated (love that word) the tumours.
The first image shows the malignancy in a later stage
The second was where I had been hoping for the best and probably was in denial about the terminal prognosis given by two 'learned gentlemen'

