Town mark is missing and it was already used at the time (St.Eligius), but striking similarity of the mark with the example in Rosenberg and Frankenburger leaves little doubt about the maker. (Unless another and later``BP`` mark emerges associated with town mark for more positive identification).
This master made ecclesial silver kept in several museums Reiche Kapelle, Munich (two monstrances - ``Monstranz``), Musées royaux des Beaux-Arts de Belgique (gilded figure of St.Sebastian).
The quality of the spoon is not consistent with his work. His ecclesial silver was of exquisite quality (enamel, precious stones). I doubt very much the engraving, being rather primitive, was done by him.
Yes, it`s a rare find, always exciting to see silver items that old. (There was a spoon here of approximately the same age made by an Italian master, also identified by ecclesial silver).