Very rare old ironstone plate

Very rare flat plate, 19th century, in iron earthenware, "dragonfly" model, sky blue background (uncommon shade) according to my research, this shade, very rarely used, is found on items from the creil and montereau factory but this pattern is referenced at the gien factory not stamped but marked intaglio (1bh6) dimensions: diameter 24.3 cm in very good condition tableware, antique tableware, antique plate, collection, decoration, earthenware, iron earthenware, gien, creil and montereau.