Donna: as Peter notes, these were a re-issue in 1903, known as the Saatjdian issue. Saatjdian was an Armenian curio dealer in Paris who had connections in the Iranian postal administration and suggested that some of the 1894 remainders be overprinted & surcharged. Examples were sent to the UPU and a small number were postally used. The intent behind the stamps was to make profit rather than postal necessity. Thus, quite a few errors and varieties were also made, although these are relatively scarce. Crude forgeries do exist. (source: 2002 Persiphila Standard Philatelic Catalog of the Iran-Qajar Dynasty, published by the Persiphila Philatelic Society/Mehrdad Sadri). For more information, and to order catalogs, visit
http://persi.com . Upper left, upper right, and lower right items, from your scans, are of minimal value due to damage.
Numbers of your other stamps, by Persiphila, and I think also Persiphila numbers, are upper middle, appears to be #344 with $10 catalog; lower left, appears to be #345A with $20 catalog (but not supposed to have any red or orange in the surcharge); middle bottom, appears to be #346, with catalog of $10.
I highly recommend the Persiphila catalogs; even though more recent editions are pricy; if one intends to make any sense of, or headway with, early Persian stamps. As the Scott catalog notes, forgeries and reprints abound.