I understand the points above that were made but I will stick to my previous conclusion that this bike is 1885. I did not determine this date based on the serial number but rather on the obvious handlebars. 1885 was the last year the two part handlebars were offered with retaining nuts. The 1886 catalog reads in part as follows- "The cow-horn handle-bar, as first applied to the Expert this season...."
This is the type that has a retaining wedge.
The two small screw holes on the backbone really are of no help dating as they were also installed post 1885.
The 1885 Expert cranks were also serrated as I can see from one of the photos posted.
Yes it is true the '85 Experts had leaf spring saddles, (Columbia Adjustable Saddle or the Columbia Swing Spring) but trying to date a Columbia highwheel bike based on the saddle can be tricky as there is always the possibility the original owner may have updated the bike to a newer saddle. The saddle on this bike is the Shire, Veeder, and Kirkpatrick patents.