I am afraid it has taken me a while to respond. Plated silver is not really my “thing” but we do have quite a lot of Mappin and Webb silverplated flatware and cutlery which sits somewhere between stainless steel in the kitchen and real silver for “best”. It is in their Athenian pattern, an Art Deco design.
In 1965 we bought 6 place settings new from Mappin and Webb. They came from stock and most are marked X but some are V or W. From this I deduce that X is probably 1965, W 1964 and V 1963. In the picture below I have added a Y which seems to be in the same series, found on a second hand piece bought some years later.
At some stage in the 1990s we added a few more new knives. These are marked Z or A. If one assumes a 26 letter cycle this would make Z circa 1993 and A circa 1994. In the picture below I also show the A from a fork which I think was bought new at the same time, though I am not positive.
In the late 1980s and early 1990s we also added some other second hand pieces of Mappin Plate in the same pattern with different date letters.
The differing layout and the variation between lower and upper case might suggest that these marks come from three distinct letter cycles but there is not enough time for this between 1931, when I think the pattern was introduced, and the dates in the 1960s and 1990s when I bought the new pieces illustrated earlier. Perhaps there was a single cycle with variations in presentation some years. In this case a 26 letter cycle would make B circa 1943 (I don’t think it is on a piece newer than the A that I have attributed to circa 1994), while G would be circa 1948 and t circa 1961.
In addition we acquired a few separate pieces and a second hand canteen for 8 of the same pattern but in Princes Plate which seems to be an earlier trade name. All the Princes Plate pieces are also marked RD 764440 at the base of the stem. I believe this number falls within the range for designs registered in 1931/2. The letters on these pieces are h, k, m and n. (Incidentally, the second k in the picture should not really be there: it is on a stray fork in a completely different pattern!)
I cannot fit these letters in with a cycle of any normal length that would lead up to the letters found on the Mappin Plate pieces. Assuming these are all indeed date letters, as they seem to be, I wonder whether there were completely separate cycles for Princes and Mappin Plate. If anybody knows when Princes Plate ceased and when Mappin Plate started to be used as a trade name it might throw further light on this and narrow down the date range for the letters on these pieces of Princes Plate.
I appreciate that this does not help much with older Mappin and Webb items but perhaps it is a start.