A good friend gave me this 1971 vintage Monroe 1651 engineering calculator.
Please watch (part 1) if you want to see the full introduction & teardown.

Fair warning: This is a half hour video of me powering on and simply putting the calculator through some calculation exercise to demonstrate its capabilities. It will be dry watching unless you’re a calculator freak like me or you enjoy watching some old nixie tub calculator porn.

<video – power & functionality>

What makes this old calculator so interesting is how much electronic computer power it had in the day. It was feature rich, agile and even small comparatively for the early 1970’s. The nixie tube display also adds a warm glow of appeal not commonly found in too many surviving electronics of yester year. Let’s don’t forget to list rare! This example of old tech is museum quality in functionality as well as scarcity. Unfortunately for this example any functionality requiring the “second function” feature is not currently working. I have my eyes and ears on the lookout for spare parts and service manuals but nothing yet. If you know of any resources please contact me, my email is in my “about me” page on ToddFun.com (a bit coded to avoid some web bots but you humans will figure it out).

I did get in contact with the original owner of this calculator who bought it for his work with aviation calculations in 1971. At the time of this write-up he is 77 years old and I’m trying to coordinate an interview with him. I have a long list of questions so if that manifests I will update this page or post a new article on this calculator.