Transitional Post 1460s

My love affair with the Post Versalog started a long time ago. The first log-log rule I ever got was a Versalog, the "green cos" variant, serial number 124729. I found it cheap at an antique mall, and the very next week found the hardcover manual for it at a different place. My dad's K+E 4071-3 had taught me the basic scales very well, and now I moved on to master the Versalog. I look back on that very fondly, and that particular rule is ALWAYS somewhere handy, has been since I got it! It's like an old friend, you know? I'm sure everyone has a slide rule like that. But it also got me interested in Versalogs in general, and that is where this post is headed.

In the picture at left we see four different Versalogs. These all have something special in common that might not be obvious to many modern collectors and users. But before I go any further, thanks must be given to one of the first people I ever communicated and corresponded with online about slide rules, and that is Mr. Ted Hume. The author of the huge research project to understand and catalog all the various variants of the Versalog, Ted kindly communicated with me several times over the years about these rules and his research. It was through private e-mails with him that I came to know just what these rules were, which I will share with you now.

According to Ted, Hemmi, for whatever reason, failed to date code a smallish number of Versalogs during the time that they were getting ready to switch to the Versalog 2 rule, around 1968. Several years ago, I had obtained one such rule, the top most rule in the picture, serial 827356. At the time, this became the lowest known rule with a serial number, but no date code. Later, I found ANOTHER of these "rare orphans" as Ted called them, the second rule in the picture, serial 900575.

At the time I got this second unusual rule, Ted's research indicated that the highest known such rule was serial number 914809. Only 9 or so such rules were known to exist at that time, but Ted felt sure more were out there. Which brings us to the slide rule that arrived in the mail TODAY.

The third rule in the picture, housed in the late type two piece plastic case, is serial number 917377, and has NO DATE CODE. This then, according to what I know as of today, becomes the highest known such "mutant" no date code/with serial number rule. In this picture, then, you can see the LOWEST and the HIGHEST serial numbered rules of this type. But wait, what is that bottom rule?

The Versalog 2 you see is one of the very first of that type made, with the date code SK which translates to November 1968, which incidentally is PROBABLY the date code that most or all of the "orphan" rules ought to have. This rule, then, is right up against 917377 in production!

Do all of your late Versalogs have date codes? Maybe YOU have one of these! No, it won't boost it's value 3000% or anything, and without a very close look you cannot tell them from another. BUT, it's something fun to look for, and thanks to Mr. Hume, I know what they are, and have had a lot of fun looking for rules from this brief period in time.


  1. My first serious rule was a Hughes-Owens Versalog
    341-3010 model. I paid $19.95 for it (new) in 1973
    and used it for important exams etc. One of my favorites, along with a Faber-Castile (my very first rule) ($1.50 at an auction)

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  3. (Husband of ktown librarylady) I have Versalog s/n 908260, no date code. Got it as a senior in high school, did my freshman aerospace engineering courses at Texas A&M with it in 1971-72. Wonderful instrument! Went to the army for two years, and when I returned there wasn't a slide rule in sight. My HP-45 saw me through my degree and my first years in the aerospace industry.
    Anyway, when I became aware of the date codes, I wondered why I couldn't find mine. Now I know. Thanks!