Drastic Cleaning Measures

Alright then, looks like long term soaking it is. Its had nearly 1 month already, so it can stay in its current container. I definitely wouldnt be happy if there was bare metal under the encrustment...

I will like the coin, hand of god and all. But if its worth £20, then ill be obliged to sell it...

This sounds extreme but I have heard of experts in the field of cleaning coins using a scalpel... not your common craft scapel (with a flat edge) but a scalpel with a curved blade.

The action they use is similar to peeling potatoes... the blade is held nearly parallel with the coin and by making small circles turns the hard stuff into dust. Obviously if you hit metal you have to stop but by breaking the surface and removing some of the deposits inbetween each soak you will speed up the cleaning process dramatically.

They all say try not to apply pressure, just lightly but repeatedly... you will know if it is working if you are producing dust.

They also use diamond dusted dental tools...but insist that good knowledge of what the coin should look like is required as you dont want to remove any details. Again its a case of light circular motions, checking regularly what you are doing.

If you havent used this technique before probably best not to practice it on an expensive coin like yours since one slip and you could do irreversable damage.

Search online and you might find some PDF files explaining further these techniques. (There is a whole book somewhere which is quite in depth and covers a multitude of techniques)