This is a Casella Model 6300 Actinograph, also known as a pyranograph.  It's shown in the 1948 and 1958 Casella catalogs available on this website.  It measures solar radiation with a combination of blackened exposed and shielded bimetallic elements, sensing a differential temperature that is proportional to the amount of radiation.  The clock has a 24 hour movement.  The inside of the case has a US Navy property sticker on it.  It weighs a hefty 28 pounds.

Go to Casella catalog page.

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