Postby JBA » Tue Feb 21, 2012 12:44 pm
An interesting question! Practice in England in general was, in my understanding, pretty similar to how you describe things in the Netherlands. The date letter was included to be certain of which assay master was responsible for marking the piece in question, in case it was found to be fraudulent and sub-standard at a later date.
I can speak accurately for London only- in the provinces practices were less... strict ;).
In England as well as Holland the date letter is actually the "wardens mark". So when the Assay Master changed, so did the date letter. This took place on the 19th of May (St Dunstans Day), and then from 1660 the 29th and each term of office was exactly a year. In 1973 this changed to the 1st of January, so modern marks are for the exact year.
But of course sometimes the assay master was changed more than once within a year due to death, promotion or (in early times) fraudulent activity. But it was not the letter of the alphabet that changed. This would be too confusing!
Usually instead it was the shape of the punch which changed. e.g. 1560, 1619, 1627 1702, 1740 However, on a few occasions a pellet, cross or dot was added, like in the Dutch system as you describe. For examples check 1567 and 1575. Usually this is to denote a change in assay master, although 1560 change was because of a change in the standard.
Not all books record these different punches- this is important to realise!
Something I have only realised on attempting to answer your question is that I can find no instances of this practice after 1740, and I have no idea why. I will read a little and see if I can come up with an answer as to what was done instead.