With the caveat that Last Dodo, sometimes, loses the plot, here is a listing of a Danzig stamp of 1925 with Michel number 214 mentioning the 'Wabe' (incorrect name) watermark and Postdruckerei Danzig.
https://www.lastdodo.de/de/items/17...-stadtwappenAnd a screenshot from another site that shows the details and watermark.

It is very interesting to see the earlier post with an article mentioning the Wuerttemberg watermark that is quite different and also no longer in use at the time.
This site shows the stamp with watermark, but does not mention the printers. This site is administered by PostmasterGS.
https://www.germanstamps.net/wmr-da...1925-smcoat/All sites show later stamps, the first two with the same watermark by the same printers.