My vase is definitely different in shape from the one in the Botterweg auction, less bulbous and a wider mouth Also, mine has 18 ribs whereas the Botterweg seems to have 19 But doesn't the one in Ricke look very like the one in the auction, yet one is by Meydam and the other by Copier? Just for for reference and interest, I've included a copy of the page from Liefkes which shows Copier vases, Serica 44 and 45, with same technique, different shape, but the Serica 45 at least is in green
I've looked at the photographs of a few Franck pieces now and I'm fairly sure I can rule him out. The similarity of the colour, the texture, and the technique keep me coming back to Leerdam.
David