6. Quality of tin marketed

Each producer markets refined pewter ingots bearing its own characteristic trademark. This may be registered on the London Metal Exchange (LME) and/or the Kuala Lumpur Tin Market (KLTM), to guarantee compliance with specifications relating mainly to chemical composition.

These specifications generally set minimum contents for tin and maximum contents for the various impurities. The best-known standards are those established by ASTM in the USA and by the European Committee for Standardization. European standard EN 610 of 1995 recognizes five quality grades: Sn 99.99%, Sn 99.95%, Sn 99.93%, Sn 99.90% and Sn 99.85% (table 6 ).

Higher purity grades (99.999% and above) may be offered by some producers but are not registered by metal exchanges.