My opinion is that this lot from a Legendary auction are all 1926 Exhibits because they seem to have the same toning and most likely the same provenance.
Link
In this lot, these cards have the box:
Sparky Adams
Max Bishop
Raymond Blates
Oswald Bluege
Max Carey
Hugh Critz
Charles Dressen
Wilson Fewster
Howard Freigau
George Grantham
Harry Heilmann
William Jacobson
Walter Johnson
Willie Kamm
Walter Lutzke
Clarence Mueller
Earl McNeely
Edwin Rommell
Ed Roush
Charles Ruffing
Ray Shalk
William Sherdell
Harold Traynor
Ernest Wingard
This seems to agree with Scott's list of what he is also missing in the 26 Exhibits set. If anyone has any of these cards without the box, if they could post this, that would be great.
I would think the toning in the 26 Exhibits would be slightly bluer while the 25 Exhibits would be grayer.