Is this real gold or not?

i have been left some gold + other items from a will. i have mens rings that does look gold , there are no signs of wear or discoleration. i have taken a knife to the back of the ring and sractched into it and it appears to be solid gold and not plated, it isnt magnetic. but the hallmarks are 18k and 750 .... the 18k hallmark is in a diamond shape and the 750 is in a rectangle shape........ i have no other ways of testing if they are real, what are your thoughts????? would you say they are real???