Pre 1990 Diedrich IR-12 cooling bin cover plate?

[Thoreauman]

I am cleaning up a very old, no digital thermometer or hi-temp etc IR-12 and don't understand why there is a plate blocking the chaff compartment as shown in the photo. The only exit would be the exhaust vent. Seems to have been there a while. Any help please.

 

[sae]

I am cleaning up a very old, no digital thermometer or hi-temp etc IR-12 and don't understand why there is a plate blocking the chaff compartment as shown in the photo. The only exit would be the exhaust vent. Seems to have been there a while. Any help please.

The cooling air goes through a hole in the back and the hand damper closes it off if you have the air set to go only through the drum. If this was open the air wouldn't pull through the drum.