Neil - my apologies for the late reply - we've been away looking after family, and are just catching up. Your pedestal footed vase (possibly a "celery") is breathtaking. It's a show-stopper! To the best of my knowledge, it is the first reported Diamond Cut piece in this specific shape. The iridescence is magnificent. Many congratulations on acquiring this beauty.
Who made it? I've gone through all our archive / catalogues etc., on Inwald and Hortensja, but I cannot find this exact shape in Diamond Cut. My "gut-feel" (based on the iridescence, the shape and the scalloped detail on the foot) is that the item was made by Inwald, but I do not have proof-absolute for that attribution.
Will you allow me to use your photo(s) in my research - fully attributed and acknowledged to you, of course? This is a splendid "find". Again, congratulations.