Understanding Gold Karat Stamps: What Does '18k' Mean?

Question
Hi there,
The other day I came across a Gold Ring that was marked '18k' and this got me thinking about this simple type of Hallmark and was it a safe mark in as far as any tom Dick or Harry can stamp a metal with a number? When was this type of simple Hallmark first used and by whom? Also is it used worldwide?

Kind regards

Peter

Answer
Peter-
the 18kt you saw is not a hallmark but a Karat stamp which should be followed by a mfg. hallmark with their logo or initials. Gold has a distinct feel and look about it and is often tested if their is question regarding Karat quality. Worlwide the stamping is usually marked with  quantity, for example:  14Kt - 585 or 58.5  pure gold and a mix of alloys, 18KT - 750 or 75 pure gold and alloys mixed etc...
all the best
Les