Heavily encrusted coin

[Jacob D]

This coin came with giant bumps that are like stone.  Anyone know what this is?  There is no part of the design that is visible and when veiwed from the edge it looks like a flaky biscuit with many layers.  Any advice on cleaning or leaving alone would be welcome.

[areich]

Hi Jacob, can you try for sharper pictures? From the ones you posted, I can't tell whether these are actually encrustations that can be removed. I'm not even sure it's a coin or ancient, though it's certainly an old, round object, seemingly made of metal.

[SC]

Whatever it is it looks like it has pockets of quasi-dormant BD.

The bright green spots look like BD under a thin crust.  They could be safe and hard malachite but somehow I fear the worst.

The brick-red bits are recent (geologically speaking) BD.

That means it won't be easy to clean, or if done so chemically could leave huge pits.  On the other hand nothing seems visible as it is.

Shawn