The Comdyna GP-6 is an analog computer from the late 1960s. The first question you might ask after looking at it is “how am I supposed to use this?” After looking up the operator’s manual as well as several YouTube videos, from what I could gather you would use various banana connectors to input information about the different variables involved in an equation, each variable set to a different “channel” of the computer, and the Comdyna GP-6 would compute the result and send it to output. Most applications I’ve found online of this computer seem to be for solving differential equations. To visualize the result of the program, you would often connect an oscilloscope to the computer (shown in this paper by Ray Spiess, the inventor the computer, on page 69).
Looking at it, you may think its relevancy ended after other non-analog computers, such as the Apple Lisa or TRS-80, were produced, but according to Ray Speiss it was in production for at least 36 years after its initial creation (p. 68). The previously linked paper goes into more detail, but essentially it was a very popular machine for teaching control systems to students in universities, as well as for a few other very specialized lines of work (Speiss p.70).