I've got a dozen gilded buttons in my collection, some large and some small. They resemble the RAF type except that the crown is more elaborate and is also topped by a cross.
Here are two pictures I took:
Some are marked "ET.s V.ve Martin - BRUXELLES", others "J. Fonson - BRUXELLES" on the rear side. To see larger pics try and save them on your desktop.
Any clues?
Franz