What if it have diamonds and mark 10kRGP?

If an item is marked "10k RGP" and contains diamonds, it likely indicates that the piece is made of 10 karat gold with a gold-filled or gold-plated finish, where "RGP" stands for "rolled gold plate." This means that the item has a layer of gold that is bonded to a base metal, offering a more affordable alternative to solid gold. The presence of diamonds suggests added value and aesthetic appeal, but the overall worth would depend on the quality and size of the diamonds as well as the craftsmanship of the piece. Always consider having such items appraised by a professional for an accurate valuation.