The colour is correct for gold...no stamp...they could have worn off...you could do your own test....but you would need concentrated hydrochloric acid,....rubber gloves..and mask,a glass container small amount of acid teaspoon is enough,drop ring in...if it does,nt change colour its gold..i,ve done it with battery acid...which is sulphuric, or you can use ascetic which is vinegar..if its plated the vinegar will make it go black....do it outside...or the safest method..take them to a jewellers as for the stone its most likely black onyx...the price of gold is sky high,