Recently picked up a 1930's Waterman Ink-Vue Demonstrator. Grand pen. We actually have Waterman documentation for it, though I must dig up the Pen Prophet (Waterman period literature) that shows it. True Demonstrators essentially are one-in-a-thousand pens, as generally a store acquired one to use along with the oodles of regular pens it so sold for years. This thing is far rarer than the better known Parker 51 and Sheaffer Snorkel demos. All I've seen have at least a yellow cast to the celluloid, and I don't know offhand if this represents the typical early ambering seen to clear celluloid or if the pens were made with that bit of a yellow tint.
I've seen maybe 5-6 of these in thirteen years collecting, counting retail websites, 80 pen shows attended, ebay hunted daily... with the caveats of course that I might overlook some and that my memory might not be perfect
I've not yet cleaned and flushed this one, but figured I'd share it. There even is a surprise in the last image.
regards
David