The LBMA label is awarded by the London Bullion Market Association to smelters that Gold bars that meet certain quality requirements. The LBMA maintains a list of all smelters in the world that meet this quality mark. It is a quality mark that is now so widely accepted that it is always preferable to buy a gold bar or coin from a producer who is LBMA certified. These products are easy to trade worldwide.
Pamp Suisse is an LBMA certified smelter, just like Umicore and Hereaus, for example
Source: LBMA