All Crop 60A

That looks like the original 1936/37 model combine, called the All-Crop Harvester (no model number). Sad condition, but uncommon nonetheless. There would be some parts interchange with a 60A, but not many. 

Not many differences that I know of. The grain bin has slightly more capacity due to it having a V shape in the bottom of the bin to accommodate an auger to convey grain to the unloading auger. Previous 60s just had a sloped bin floor to funnel grain into the unloading auger. 60As also have a lever actuated jaw type clutch to engage the unloading auger, where the 60s had a knob that must be turned to engage a dry disc clutch, and they notoriously slip when worn.  A 60A brochure says they improved the cylinder/header drive gearbox on the 60A, but I don't know what that entails.  

If there is a perforated sieve/screen, it will be basically at the bottom of the RH rear stack of racks at the rear of the combine. Stand outside looking down the straw rack (sideways/across the combine) and then go down to the bottom of all the racks/trays. There may be a removable one at the very bottom - or there may not. They are commonly removed  or some crops like oats didn't require an additional screen.

I wonder if the screens are the same size as used in the later All-Crop 60, 66, and 72?