In his A Guide Book of Counterfeit Confederate Currency, Tremmel has this to say about Upham and other counterfeiters.
"One approach for estimating the amount of counterfeit Treasury notes circulating in the South begins with the claim Sam Upham made to Dr. Lee that he produced $15 million in 'facsimiles' (approximately 1.5 million notes) during the 16 months his counterfeit business was in operation. To this amount several 'conservative best-guess' adjustments should be made. (A 'conservative' estimate, in this case, means quantity estimates that are at the high end of the range.) Since Upham was not alone in the 'facsimile' business, some amount must be added to include the notes placed into circulation by other counterfeiters.... For the next step, assume that Hilton, a major producer who was in business for roughly the same period as Upham, issued a quantity of counterfeits similar to Upham's output. Also assume that all of the other counterfeiters collectively added another $15 million. So, a conservative best guess might increase the initial $15 million by three times, to $45 million.
"Consideration also must be given to the fact that not all counterfeit/facsimile notes 'went South' and entered circulation. Some actually were kept as souvenirs while others were discovered and confiscated. As another best guess, assume 80% entered the Southern economy. Combining the above estimates and assumptions indicates that up to $36 million in counterfeit notes circulated during the war. Assuming a face value of the typical counterfeit at $10 to $20, this averages out to 2.4 million spurious notes in circulation.
"To compare the total dollar amount of counterfeit currency to the total dollar amount of Confederate currency issued is fairly straightforward. As mentioned above, Confederate Treasury Department records show that $1.554 billion in currency was issued, net of currency retired or recalled. Adding to that $130 million of state, bank, local, and private currency, also mentioned above, gives a total currency supply of $1.684 billion. The percentage of counterfeit to the total of genuine currency, then, is 2.1%. This is admittedly a crude estimate and possibly on the low side. So, to make the estimate even more conservative and allow for a 50% undercount of counterfeit notes, double it to 4.2%.
"In 1999, a related study was published, entitled 'Bogus Money Matters: Sam Upham and His Counterfeiting Business.' It was written by Marc D. Wiedenmier, an economics professor at Claremont McKenna College in California. Wiedenmier measured the impact on the Confederate money supply of Sam Upham's counterfeiting during the 18 months Upham was in production. He estimated that if 100% of Upham's spurious currency entered the Confederacy, that amount, as a percentage of the growth of the money supply ($541 million) of only the CSA Treasury notes, would have been 2.78%. For the same 18-month period, Wiedenmier's study indicated that the percentage of 100% of Upham's counterfeits would have been 2% of the total money supply of Treasury notes ($749 million).
When adjustments are made for non-Treasury currencies, non-Upham counterfeits, and a 'souvenir' allowance of 20%, Wiedenmier's counterfeit-currency amount, as a percentage of the total money supply, is 4.8%----a reasonably close match to the previous rough estimate of 4.2%.
"So, while certainly meaningful, the estimated percentage of counterfeit currency in the money supply does not seem significant enough to have been a major factor in the large drop in Confederate currency purchasing power."