Brad - This is the recirculated heater that I originally pulled out of my '51 3100.
http://farm9.staticflickr.com/8089/8493674450_171e80f3bc_b.jpg
http://farm9.staticflickr.com/8091/8493674478_287a922071_b.jpg

My memory failed me on the construction but the color is definitely darker.


And to keep this on topic, here are a couple pics of the fresh air heater I am replacing it with.
http://farm9.staticflickr.com/8088/8493726672_0648bfd6e1_b.jpg
http://farm9.staticflickr.com/8369/8492625865_153faa15d7_b.jpg