One of the more interesting, and rare, items in my collection is the National Time Computer. This is a device that is used to determine the number of days from one date to another or to determine the date from a specified number of days from the chosen date. It is mechanical and consists of a main cylinder encased in a metal shell with a smaller dual counter mounted on the outside. It is meant for desk top use and measures in at 9.75”L x 6.75”W x 4.75”H.
This is an item for which there is no information that I could find on the internet. Finally I came upon a reference to a similar machine in a book titled “Antique Office Machines: 600 Years of Calculating Devices” (Thomas A. Russo, Antique Office Machines: 600 Years of Calculating Devices, 1st edition, Atglen, PA, Schiffer Publishing Ltd, 2001). On page 122 of this book is the same device but built by the H.H. Allison Company of Sac City, Iowa. However, it was just a picture with no further information. Knowing the name of this company I took a chance that it was named after the inventor and started some new research. This turned out to be a correct hunch because the time-computer was indeed patented by Henry H. Allison. He was awarded patent 1237271 in August 1917. He started the H.H. Allison Company and the time-computer was one of the products he originally sold.
I assume that some time later the patent was either licensed or sold to the National Time Computor Company of Fairmont, Minnesota. The label on the National Time Computer states that it is patented so I feel I can safely state that this item was made after 1917. My time computer even has an additional cylinder for leap years.
At first glance you may think that this isn’t a very useful item, but you’d be mistaken. There are many professions and organizations that would find this to a great time-saver. Government agencies, lawyers, banks and real estate come to mind.