I enjoyed Robert R. Van Ryzin's article about the 1913 Liberty Nickel - a great read! I don't know much about the back research on these coins but I put a few keywords into Newspapers.com and came up with this 1920 reference.

I found the same article in a different publication and this time dated 6 days earlier! This may help to better date the dinner which he says occurred "last night."

That is the correct address for Dunham per a 1920 issue of The Numismatist. It looks like it could be a possibly mixed-up reference to Brown's nickel. The $600 figure certainly fits, as does "without a Buffalo".

Brown left his nickel at the convention on Aug. 22. The dinner was on Aug. 24 -- one day before one of the two newspaper articles. Dunham is listed as being at the banquet. Brown was not.

Nothing I've seen links Dunham to the nickel, and as Brown apparently asked for it to be sent back, as reported in the January 1921 issue of The Numismatist, I doubt Dunham owned it at that point.

My only guess would be that Brown had more than one there and sold one to Dunham? -- but that would be a really wild and unsupportable guess. There's no record of Dunham ever having one that I know of.

Mixed up or not, surely an intriguing find.