What is 875 jewelry marking?

what does 875 on jewelry mean? actually i have never heard of 875 in jewelry,which when there is such a thing as a number in gold , 585 which means 14k,or 417 meaning 10k,or 750 meaning 18k etc,but never heard of 875.

.875 marked on gold jewelry would indicate 21 karat gold. It isn't that common, but sometimes seen.
If marked on silver, it would indicate something a little less pure than sterling silver, which is .925 (meaning 92.5 % pure)
So, in either case, .875 means 87.5 % pure.