I mentioned having an 1874 tissue copy of a letter by an early sports figure. This is the first time I had a tissue copy like this in, so I did some research. I found an article over here at www.officemuseum.com. Here is a slightly abbreviated version of the article:
Letter Copying Presses
A few alternatives to hand copying were invented between the mid-17th century and the late 18th century, but none had a significant impact in offices. In 1780, steam engine inventor James Watt obtained a British patent for letter copying presses, which his firm manufactured. The patent illustrations include a press with two opposing rollers, like the wringer on an old washing machine, and a second model with a screw mechanism like that in Plate 1. However, the presses produced by Watt were portable devices contained in wood boxes similar in size and appearance to the late 19th century Edison Mimeographs.
Although use of letter copying presses was initially limited, by the late 1840s copying presses with a variety of screw and lever mechanisms were widely used in offices to copy outgoing correspondence. Along with typewriters, letter copying presses are the most common machines found in photographs of late 19th century and very early 20th century offices. (See plates in the Early Office Museum’s photograph exhibit.) Screw model letter copying presses were still marketed in 1950.
In a review of office equipment at the 1851 Industrial Exhibition, Granville Sharp recommended that when an office was selecting a press like that in Plate 1, it should make sure that the handle was heavily weighted at the ends to insure proper spinning. “This is essential to a screw copy press; for unless one pull will serve to raise or to depress the plate, much time is lost.” In addition to the press, offices needed to buy copying books that contained up to a thousand pages of tough tissue paper, copying ink, copying paper dampers, oiled paper, and blotting paper
Sharp explained that before using the new press, the office had to decide how to organize its letters. Production of copies was easiest if the user copied its letters into a single letter book in chronological order. In that case, the user needed to make an index so that letters of interest could later be retrieved. Alternatively, the office could organize its correspondence by client, which avoided indexing but made it necessary to use numerous copying books on a given day.
Although copies could be made up to twenty-four hours after a letter was written, copies made within a few hours were best. A copying clerk would begin by counting the number of letters to be written during the next few hours and by preparing the copying book. Suppose the clerk wanted to copy 20 one-page letters. In that case, he (copying clerks were men) would insert a sheet of oiled paper into the copying book in front of the first tissue on which he wanted to make a copy of a letter. He would then turn 20 sheets of tissue paper and insert a second oiled paper. Sharp advised that “Success in copying letters depends almost entirely upon the damping of the paper. The paper should be saturated and damp, not wet.” To dampen the tissue paper, the clerk used a brush or copying paper damper. The damper had a reservoir for water that wet a cloth, and the clerk wiped the cloth over the tissues on which copies were to be made. The oiled papers confined the moisture to the pages that were to be used. Blotting paper was used to remove excess moisture.
Next, letters were written with special copying ink, which was not blotted. The copying clerk arranged the portion of the letter book to be used in the following sequence starting from the front: a sheet of oiled paper, then a sheet of letter book tissue, then a letter placed face up against the back of the tissue on which the copy was to be made, then another oiled paper, et cetera, “oiled paper being in all cases placed next the damp paper, to prevent the ink forcing beyond the paper intended to receive it.”
Finally, “Close the book, put it into the press, and screw tightly down, letting it remain a minute or two under pressure, when the copy will be properly taken, and may be dried with blotting paper, or held near the fire.” Based on experience, the clerk could adjust the press time. If he made a copy soon after a letter was written, only a second or two was needed to make a good impression. When the letter book was pressed, some of the ink transferred from the letters to the moist tissues in the book. Because the ink penetrated the tissues, copies could be read from the front sides of the tissues.
By the late 1880s, the method for moistening pages in copying books had been improved. Rather than using a brush or damper to wet the tissues, the clerk inserted a thin moist cloth or pad between each oil paper and the following tissue. A supply of moist pads was prepared in advance using a copying bath. Examples are Tatum’s Ideal Copying Pad Bath, which was patented in 1887 (Plate 6), and the Globe Roller Copying Bath, which was marketed in the early 1900s (Plate 7). To prepare a supply of moist pads using the Ideal bath, the clerk removed the tray from the bath, poured water into the pan, and replaced the tray. Also, the clerk sprinkled a set of pads, let them stand overnight, and then placed them in the tray. “The evaporation from the water underneath will generally be sufficient to keep pads damp enough for ordinary work.”
I'm finding that the general consensus is that the signatures on these tissue copies of letters are not considered actual signatures for collecting purposes --one collector/dealer went as far as to compare them to xerox copies --but this is a bit extreme because they were created within 24 hours of the original and are unique copies (only one copy would have been made in this manner).
For example, the letter I have would be worth at least $800 to $1200 as a manuscript letter, while it's likely that the tissue copy will only get between $150 and $250.