Is this Ring Solid Gold?

I found an old looking wedding band and it has the markings KM 99 925 C. I have already done a websearch and it seems it is gold plated silver however the ring is quite scratched and battered yet has no chips or exposed silver.

Is this solid gold? I'm not too bothered if it is of any value, just a little curious as to how this ring turned up in my home unnoticed. If it is gold I will need to find the owner and return it to them.
Apologies if i have come accross a bit thick but this is really not my field. Any help would be appreciated.