Art Deco Walter Von Nessen Cocktail Cups

Here's a pair of Art Deco copper and brass cocktail cups in my collection. They are attributed to famed industrial designer, Walter Von Nessen, circa 1930's. Possibly a Von Nessen studio item. I've had others tell me they are a Von Nessen design, but I've never seen any official documentation of this. They are unmarked and have cork bottoms and most likely had crystal glass inserts at one time.

The cobalt glass and chrome version of these cups in my collection are shown here:

http://www.collectorsweekly.com/stories/155116-art-deco-walter-von-nessen-cocktail-cups?in=user