Mendenhall's Practical Calculator

Active selection in cart:
This patent model for an adder has a brass box with a rotating disc inset in the top. There are 100 small holes around the rim of the disc. Outside the disc, on the top of the box, is a circular ring numbered from 01 to 99, with a gap at 00. Outside of this are three rings of holes, with 100 holes in each ring. These holes are to be used to hold markers indicating digits carried when the disc makes full rotations. On the side of the box is a rotating multiplication table. Date: 1860s. Record ID: nmah_690836.

Free public domain image

To download this free image, please register (this takes just 30 seconds) or log in.

This is one of 1,687,038 free hi-res public domain images, selected from major public collections to complement the Look and Learn archive, and to save you time and money. Typically, it may be used for any purpose, but users should check the precise terms and satisfy themselves that the intended use will not infringe the rights of any third party.

Can we help?

Look and Learn is one of the world’s leading sources of historical and cultural images for personal and commercial use. Feel free to contact us with any questions or requests.

Links