To me it looks like a good ground dug enameled RZM era badge. That said, the condition, especially of the reverse, is very poor so it's hard to really make out anything further. As for cleaning? I would have tried removing the worst of it with a toothbrush and some washing up liquid --- perhaps citric acid if it's really stubborn (very gentle)?
Did you buy this or dig it yourself?
I bought for a small price
Ok, you're welcome.
Im afraid about enamel also thanks for options
Be gentle with it and don't use any force while cleaning and I reckon it will be OK --- it's a relic anyway and will never be anything else so no point in over-cleaning. Nicely representative either way!
good ground dug.