galba68. Your clean-up job, of a Celtic drachm, may have been worthy of merit. It looks fine, in the photos after cleaning. But, sorry, we haven't seen what it looked like before cleaning - unless there were photos that escaped me.
According to your post received yesterday, galba68, your Celtic coin was truly in a rotten state. Not for me to judge the rightness or wrongness of the cleaning process, can only say it looks like you've done a great job. Now,your Celtic coin appears to be alright to display, whereas, earlier, it must have been a Cinderella of your collection.