A hallmark is a mark stamped on objects of gold, silver or platinum which certifies a 'guarantee' of standard purity (e.g. 800 silver 925 silver). Theoretically, all items of solid precious metal should be hallmarked by an assay office of the region of manufacture, however, there are cases in which some items are not stamped, have been erased or in some cases faked.
We use the term 'guarantee' in the context of hallmarking loosely at Artisan Antiques due to the fact that a hallmark stamp can be relatively easily faked. We ensure the authenticity of our antique items though numerous analyses including acid testing, backtesting manufacturing notes, etc. Our advice to all collectors is to look at hallmarks as the final check on precious items - we highly advise all our clients to conduct research first, obtain knowledge of what is being purchased, then proceed to check hallmarking to finalise the analysis of an antique item. This way, you ensure that you are not solely relying on one mean of certification and can minimise the chance of buying a misleading/unauthentic item.
Above are some hallmarks of English silverware. An English Silver lion, lion head (London assay), maker's mark, date mark and Georgian head are present.