I’m no expert but per Belleek.com: Third Period Black Mark – 1926 – 1946 Introduced in 1926, possibly to mark the Wembley Exhibition of that year. It also contains the registry mark “REG No 0857”. Interestingly this registry mark dates from 1884 but was only used from 1926! This mark is always black and was used up to 1946. Around scroll with Celtic decoration and the words “deanta in eireann” (made in Ireland) added. On Earthenware the stamp Belleek changed to “Melvin Ware” in 1936 probably to distinguish it from the more prestigious Parian China.