I received a very fast reply from Peter & Monika today:
Sehr geehrte Frau Pearce,
die Vasen sind nicht von uns.
Wir wünschen Ihnen ein schönes Wochenende und Frohe Weihnachten
Monika und Peter Kaspar
So the vases are not made by them.
Sometimes illimination can be as useful as considering a probable or possible maker, however, we sill don't know two things... one is, are these genuine signatures, and the other, (possibly of less importance), is, why has the same buyer now put the same vase up for sale three times?