One of the pieces possibly compared with this piece is the famous gold fibule the Empress Gisele wore during her wedding with Emperor Conrad II in Rome in 1027.
For another quite similar Hungarian silver-gilt piece by Paulus Kirtscher, circa 1596-1609, with enamels, turquoises and precious stones, see Bernard de Leye catalogue, nr 916. One could think this piece dates from years 1400-1430. Dutch researcher, Professor Karel Citroen, attributes the inscription to Alle de Haas, Sneek in Friesland, between 1877 and 1923.
On a bronze medal representing Queen Euphémia of Denmark's tomb (who died in 1330), for Soroe church, west of Copenhagen, the Queen wears a similar clasp on her bust.