Weston Photronic (Universal) Exposure Meter Model 650: 1935, USA manufacture. 

This was Weston's alternative design to the model 617 type 2. The side by side arrangement of meter and dial may have seemed like a good ergonomic alternative to the up-and-over design of the 617. Time has proved that the 617 was the better arrangement. However, the 650 does have space for the iconic Art Deco fan feature arranged around the meter needle pivot. Coupled with the truncated edges, this styling represents an unashamed adoption of the 30's Art Deco movement. The fan shape is replicated in Weston's direct reading exposure meter.

Some variations of the calculator dial and back scribing plate can be found in examples collectable today. As emulsion speeds increased, the limit of 64 Weston on earlier dials was extended to 250. Pictures of the variations are below. This model - along with its Leicameter and Cine variants - is a popular collectable today due to its Art Deco styling.

The characteristic Art Deco fan moulding on the Model 650

The 'green' dial variant: This is the first type to use the term 'Universal' indicating its suitability for both still and cine cameras. The green is not original to its production, but the result of verdigris that has built up over the years - and can be cleaned off.

Early and later examples of the Weston Model 650. To all appearances identical, but the older one (left) has an emulsion speed listing of 64 Weston maximum. The later (right) example extends this to 250.

Three variations of the back plate of the Weston model 650. Speeds for proprietary manufacturers are listed on early models. As the number of plate and film types grew in the '30's, this was replaced with a panel for the user to pencil in their own film speed reminder. It is interesting that no Kodak products are listed on the early model. This is probably because Weston felt that Kodak could be trusted to specify accurate ratings. There was a tendency for smaller producers to over-rate their emulsions at the time - so Weston listed their own ratings. Although panchromatic films were sensitive to red light it was very reduced - hence the different values for tungsten illumination - which contains a lot of red light.