What Does KP Mean on Gold?

The letter P after a karat number stands for 'plumb,' used in the older sense of exact or true — as in a plumb line. A 14KP stamp certifies that the piece contains at least 14/24 gold by weight, or 58.3%, with no shortfall. The mark is a stronger claim than a plain karat stamp was at the time it appeared, not a lesser one.

The mark has a specific legal history. The US National Gold and Silver Stamping Act of 1906 originally allowed marked gold to fall as much as half a karat below its stamp once solder was accounted for, so a piece marked 14K could legally assay closer to 13.5K. The Gold Labeling Act of 1976 tightened this tolerance to three parts per thousand (seven parts per thousand including solder). Manufacturers began adding P to advertise that their gold was 'plumb' — full karat — and the mark is most often seen on American jewelry from the 1970s and 1980s.

The most common misreading is that KP means 'karat plated.' It does not. Plated pieces carry marks such as GP, GEP, HGE, or RGP; a KP stamp indicates solid gold throughout.

For value purposes, 14KP is simply 14 karat gold. Because modern marking tolerances are now tight everywhere, a KP piece is not worth more than an honest 14K piece of the same weight — the mark mainly helps date an item and confirms it is not underkarated.

Look for KP marks in the same places as ordinary karat stamps: inside ring bands, on the clasp or jump ring of chains and bracelets, on earring posts, and on the backs of pendants and brooches. The mark usually reads as a karat number followed by KP — 10KP, 14KP, or 18KP — sometimes with a maker's mark alongside. A jeweler's loupe helps, as the stamp is often under a millimeter tall.