I can't give you an exact date or details, but I can tell you what I found on the internet. Gowland & Grant was a retailer in Sunderland, England. I found an auction for a Silver Salver that had the stamp. The auction house stated that it was from 1927. They did not make the piece; they are the retailers. It was common for high-end sellers to have fine pieces stamped with their name. The number you describe is most likely a pattern number. All the pieces of the set would have consecutive numbers showing that they belonged in a set of that pattern style. I found a "genie's lamp" stamp. A maker called Robert & Belks used it, but I can't find any information on that maker.