Weston Ranger 9 Universal Exposure Meter Model 348. 1966, USA manufacture.

A close up of the calculator dial on the rare Ansel Adams variant of the Ranger 9.  The multiple pointers on the outer dial have been moved to the outer edge and the Exposure Value (EV) scale has been replaced with a sequence of grey tones which correspond to Adams' Zone Systerm for determining exposure.

This detail from the Ranger 9 instruction book illustrates the push-fit Invercone. 

Below is an illustration of the Ansel Adams Zone Exposure system stepped ten level wheel. Weston say this will become available as an accessory and it is clear that, as designed, it is not the disc that is actually fitted to the A.A. variant. This artist's impression has probably been created ahead of the actual dealer fitted option becoming available.