Weston Ranger 9 Universal Exposure Meter Model 348. 1966, USA manufacture.
A close up of the calculator dial showing a model where the outer multiple pointer dial has been over-pasted with an overlay designed for use with the Ansel Adams Zone System. The multiple pointers on the outer dial have been moved to the outer edge and the Exposure Value (EV) scale has been overlaid with a sequence of ten grey tones which correspond to Adams' Zone System for determining exposure.
This detail from the Ranger 9 instruction book illustrates the push-fit Invercone.
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Below is an artist's impression of the Zone System overlay as it appears in the manual. This must have been published prior to the actual overlay becoming available, as the actual crescent stick-on panel is very different in design.
There is some speculation around how this particular model, the 'Ranger 9', got its name. The most likely reason concerns the U.S. Ranger space missions. These were a series of uncrewed lunar flights where the probes were designed to crash onto the lunar surface, taking highly detailed photographs as they went. The last probe in this programme was the highly successful Ranger 9 in 1965.
So, what better reason in 1966 could Weston have than to honour the Ranger Lunar Programme when launching (on earth, that is) their new innovative exposure meter? And why the designation of the number 9? Well, there were 9 probes, so maybe that's it? Most of them were unsuccessful but the last of the series, no.9, was. But then space programmes are not normally remembered for the number of launches (we don't call the Apollo programme Apollo 17, for example). So maybe there's another reason for using the number 9 designation: The CdS-based meter is capable of measuring much lower luminance levels than the Selenium-celled models. Weston might wish to emphasise that when naming their new meter. So, if you take 1 candle per square foot as the reference point on the meter scale, in stops, it goes right down to 0.002 Cd./Sq.ft. An that happens to be exactly 9 steps. So the meter 'Ranges' down '9' stops.
What, of any of these, are the answer? You choose.
Now here's something you don't see everyday. Doing a search on 'Weston Light Meters', the very last item I came across was this: a brand new manufacture vinyl overlay for the Ranger 9 to support the Ansel Adams Zone system. As illustrated, it's made by James Rinner and it shows that there is still a great interest in exploring and using exposure meters such as the CdS Ranger 9, still working after 60 years!
And it's not just the Westons that James supports. If you're interested in Pentax or Sekonic spotmeters, he does Zone overlays for those as well. See his Etsy webpage HERE. His Ebay site is HERE. And the instructions for fitting the Ranger 9 overlay HERE. Oh, and by the way, he also makes other accessories for a wide range of vintage and modern cameras (see his Etsy and Ebay pages). Well done James for supporting traditional photography!