I don’t know if it’s the same seal, but there’s one on Twinings tea, and I think there’s one on Carr’s crackers.
Many UK products are manufactured “By appointment to the Queen” (or some phrasing like that) and are entitled to display the seal. AFAIK it just means that somebody at the Palace saw one once, and the company applied for the patronage label as a marketing ploy. It doesn’t really mean much.