This post has been updated during the day on March 16 to take into account a late contribution by Malcolm Goldstein.
Readers have come up with two possibilities for the identity of E. E. Hamilton.
David Thompson found Mr. Edward Elwood Hamilton, of the Baltimore, Ohio and Southeastern Railroad. There is a write up on him in the Baltimore and Ohio employees magazine upon his promotion to head up analysis and statistics for the railroad. It is possible, but it seems a bit strange that his position would have him canceling many 2 cent stamps, so I'm not sure. However, we do have this picture, with the appropriate initials and name:
Meanwhile, Malcolm Goldstein found that an E. E. Hamilton was the Secretary and Treasurer of the New Castle [PA] Traction Co. I can't find much more on this lead, but it would seem that this E. E. Hamilton (and maybe they are the same person) would have used more 2 cent documentaries. A little more digging is at hand.
And Malcolm kindly did so, and came to this conclusion:
A further Google search makes me think that Dave Thompson and I have found the same person. In 1898, Hamilton was in New Castle PA, north of Pittsburgh, connected with a traction company. As you are undoubtedly aware, a traction company was a streetcar, or possibly an interurban railway, company. The new search, coupling Hamilton's name directly with the B&O Railroad, shows he resigned that position in 1902, and in 1903, an EE Hamilton is an incorporator of a small railroad in Castle Shannon, PA, which is a small town south of Pittsburgh. That small railroad was, in turn, a feeder line to the B & O Railroad, and by 1904 an E E Hamilton was a "freight inspector" for the Wheeling W VA division of the B&O Railroad. He seems to have moved up through the ranks at the B&O at least until 1919, and then, in a 1934 Report to Congress from the Chairman of the Interstate Commerce Commission, his name reemerges as the "executive assistant" to the President of the M[Missouri]-K[Kansas]-T[exas] RR, who served on some federal advisory panel to prepare a technical questionnaire to collect shipping data needed to assess the need for further federal regulation of railroads. Sounds to me like the same guy all the way through.
Thanks to Malcolm and Dave. My guess is that we are almost certain to have a set of 2 cent documentaries on checks issued by his urban railway employer. It would be great if somewhere there were some of those checks still in existence.