Lately, I've come to the conclusion that I'd like a wristwatch with a slide rule bezel. I've spent plenty of time playing with slide rules so I'm pretty proficient with their use. Having one on my wrist would be nice.
I've spent time, at various department stores and jewelry stores, explaining to sales clerks what they're good for. Travelling in a foreign land? With a foreign currency? Set the slide rule to the currency exchange value and quickly convert prices between currencies. Simply find the "local" price on one scale and see the other price on the other scale. Are they using metric? And you'd like quantities, distances, etc. in imperial units? Or vice versa? Set the slide rule for the appropriate conversion factor and you're good. If you know what you're doing, you can even do more complicated conversions, like Chilean Pesos / liter to US Dollars / gallon. Or Norwegian Kroner / kilogram to US Dollars / pound. I have done these, and many more, at various points in my life.
There are a few problems with most slide-rule-bezel watches:
- Most of them put 60 at the 12 o'clock position. That's useful for doing time calculations. I don't anticipate doing that very often. I'd like the 10 at the 12 o'clock position. That way, I can use the minutes on the watch face to calculate logarithms (anyone who's used the L scale on a slide rule, in conjunction with the D scale, knows how to do this). And I don't want any other values cluttering up the space between the minutes and the inner scale. For me, at least, that just gets in the way. I've managed to find one Casio watch where the inner scale moves, so I can line that scale up with 10 = 12 o'clock. For most watches, the outer scale moves and the inner scale is fixed, with 60 = 12 o'clock.
- With all too many of them, the numbers on the scales are just too small for my aging eyes. I'm looking at you Casio and Seiko.
- The slide rule bezel is more of a marketing gimmick, so they don't put much effort into being accurate. As an example, line up the 10 in the inner scale with the 10 on the outer scale. Do the numbers line up, all the way around the dial? For some of the lower-priced watches, the answer is "no, they do not." Now, line up the 10 on the inner scale with the 30 on the outer scale. Do the multiples line up? On all too many, the answer is, again, "no, they do not." Which means any calculations you attempt will be inaccurate.
Here's my wishlist, in order of decreasing priority:
- Accuracy. Must pass both of the aforementioned tests. Otherwise, it's just "marketing" (translation: lying, bait-and-switch, etc.).
- Numbers on the scales are large enough and high-enough contrast that I can see them without needing a magnifying glass.
- Either the inner scale has 10 = 12 o'clock OR the inner scale moves so I can set it that way. If you absolutely must put time-conversion numbers on one of the scales, put it on the outer one, preferably outside of the slide rule scale. I want the slide rule scales as close together as possible to limit errors caused by parallax.
- No excessive ornamentation getting in the way of the minutes tic marks. I want to be able to see them very clearly so I can calculate logarithms.
- A complication (secondary, inner dial) showing time in an alternate time zone (UTC), preferably on a 24-hour scale.
- Solar powered, so I never need to change the battery.
- Ability to read the time in the dark
Anyone know of a watch which fits the bill? Citizen makes some which fit most of these, but not #3. Casio makes one which fits #3, but fails on #2 (possibly #1 as well).