Unusual chronograph scales

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I came across this watch on eBay this morning and noticed something I hadn't seen before: a scale on the main dial divided into 20 graduations (see photo below).

I have seen pulsometers and telemetre scales and slide rules etc but can't figure out what this one was designed to measure. Is it perhaps some kind of non-decimal production scale?

It got me thinking, are there any other unusual chronograph scales that we don't see often, and if so, what is their purpose?

 
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I came across this watch on eBay this morning and noticed something I hadn't seen before: a scale on the main dial divided into 20 graduations (see photo below).

I have seen pulsometers and telemetre scales and slide rules etc but can't figure out what this one was designed to measure. Is it perhaps some kind of non-decimal production scale?

It got me thinking, are there any other unusual chronograph scales that we don't see often, and if so, what is their purpose?

It's not uncommon - that's a telemeter scale in kilometers. 馃憤

Here's the Speedmaster version...
 
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The red scale on this Jardur qualifies as unusual. It is used to calculate an airplane's turn in degrees, based on a standard turn rate of 3 degrees/second.
E2E6570A-B19C-4926-B84B-A16ABBEDA3CA_zpst8ftfb1u.jpg
 
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The respirations (breath register) scale seen here is unusual...

Good one. Here's another:
FB28E01C-B515-490F-8BA7-C25B54829184_zpsy93cebdw.jpg
Edited:
 
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I was going to post the film one. Just missing the fraction of time bezel. With the 0-100 bezel and for some reason I can't find one.
 
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This one came from modest_proposal a couple years ago.

Thanks, David!

Your photography skills are awesome Rich, what equipment do you use to get that blurry effect?

馃榿
 
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The respirations (breath register) scale seen here is unusual:
respirations.jpg
chrono.jpg
(thanks)
5 breaths, very good for yoga.
Great thread idea, by the way

Curious, what's a "decimal scale" and how is it supposed to be used ?
Edited:
 
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Your photography skills are awesome Rich, what equipment do you use to get that blurry effect?

馃榿

Lulzz I used a potato.

I bought that watch from David (Modest_Proposal) on eBay. I had no idea it was him until after I received the watch - he always holds the watch head in his handsomely manicured hand and I recognized his fingers lmao

(I don't think he was as excited as I was when I made the connection). 馃憥馃憥馃憥馃憥
 
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Curious, what's a "decimal scale" and how is it supposed to be used ?
Decimal scale is used when you need to know the percentage of a minute. So instead of 30 seconds you have .5 minutes. Science, some navigation, factory timing and a few others.
 
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Decimal scale is used when you need to know the percentage of a minute. So instead of 30 seconds you have .5 minutes. Science, some navigation, factory timing and a few others.

And rallying / similar competition (sometimes) 馃憤
 
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Here is a sample of the ultra-rare (dare I write prototype?) double-tachy scale designed for people with two automobiles.



It might work with SUVs, too.

馃槜
 
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Decimal scale is used when you need to know the percentage of a minute. So instead of 30 seconds you have .5 minutes. Science, some navigation, factory timing and a few others.
Thanks @Foo2rama, I now feel so well informed! (I'm realizing I like toolwatches for their technical looks and often tend to ignore function... )