Sorry - I didn't read your original post properly. The 'coating' would be more than a little odd for Danish glass - although recorded glass from Holmegaard of this period is very fragmentary, and there was a lot of experimentation with a lot of items that do not appear in their standard catalogues - so I wouldn't entirely discount it.
Is it iridescence, this coating?
I had a look through the Venini 'Blue Catalogue', and I couldn't find a match there. But, again, this is an incomplete record of early Venini output.
That said, I still don't *think* it's Venini - my main arguments being that 1920s-30 Muranese soffiato glass tends to be much more thinly-blown than this vase, and that the smokey-brown of Venini, CVM and the Zecchin-Martinuzzi works is more delicate and golden-yellow in tone, broadly speaking, than the rustic red-browns prevalent in Northern European glass.
Happy to be wrong, of course!