In a small booklet ("Stop to Think") published in 1895, Felt presented a brief explanation of the machine's operation and proceeded to list some 49 customers who had purchased 2 or more Comptometers AND reprint 15 pages of glowing testimonials.
While it comes as no surprise that the U. S. Navy had purchased 9 machines at this early date, Felt's international aspirations were clearly visible as well. Beyond America's shores, the British India Colonial Government was using 6 while the Republic of San Salvador had ponied up for no less than 8!
When I had the case of my woodie restored recently, the refinisher remarked that the wood was "Honduran mahogany". It seems likely to me that, with Honduras and San Salvador being close neighbor countries in Central American that Felt had set up some trade agreement to exchange Compts for the mahogany needed for his cases. This could account for so many machines showing up in a rather obscure corner of the world, especially considering the date of 1895, only 7 years after the first Compts were manufactured, with no more than 2-3000 machines having been produced by that time.
By 1904, Felt had abandoned his Comptograph efforts, patented his metal case design and introduced the A-model with a completely re-engineered mechanism. With the ability to peform reliable multiplication much faster and a fresh look, this machine produced some significant orders including no less than 102 machines from the prestigious Marshall Field & Co. of Chicago and 86 from the U.S.Navy. However, the company was happy to accomodate the smaller customer as this 1923 envelope can attest.
Over the ensuing years, the Comptometer prevailed in almost all major businesses in America and abroad where its ability to provide fast, accurate calculations made the key-driven calculator the data processing "machine of choice" well past the middle of the twentieth century.