Not made by Felt & Tarrant, then not a Comptometer

In 1920 the company behind the Comptometer published an updated edition of their 1914 book "Applied Mechanical Arithmetic as practiced on the Comptometer". This ~600 page book was intended to help sales of the Comptometer to businesses. After a general description of the basic operations of the machine, it gives detailed examples of business calculations and how the Comptometer could make the work-flow more efficient in various industries. With extensive examples of companies' business forms and data shown, it gives a perhaps-unique peek into business information-technology of the early 20th century.

Comptometer sales-numbers by the 1910s had started to pick up, from a very slow start in the late 1880s, but in 1911/1912 the Burroughs company launched a near-identical competitor product. Hence F&T's insistence that they are the only 'real' Comptometer (that risked becoming a generic name for a key-driven calculator). The line "If it's not made by Felt & Tarrant, it's not a Comptometer" is in the footer of every page.

There are several pictures in the book that show Comptometers as used in various offices. (And also some clearly staged scenes to illustrate a workflow.) For example; a page in the section on wholesalers:

A picture is included showing a wholesale office using Comptometers:

But there's something unexpected in this picture. Quite visibly in the front of the view are two of the competition Burroughs copycat machines.

Must've slipped through, probably simply not spotted. Those Burroughs machines were the reason for that line at the foot of every page. Felt & Tarrant also filed a patent lawsuit against Burroughs about this machine - forcing Burroughs to withdraw it from the market. (Burroughs however re-designed and introduced a new, smaller machine and stayed in the key-driven calculator market.)

In their operation and in how they are used in the information-workflow of an office the Burroughs Calculator and the Comptometer are identical. However, as the footer drives home on every page: they're not made by Felt & Tarrant, so they are not Comptometers.