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?

I have an odd request...would you be able to get the serial off this combine? It's in front of the grain bin stamped on top of the angle iron frame. There aren't many of these 1935-1937 All-Crop Harvesters left, and I haven't seen a 1935 model to date, and only two 1936 machines. Several 1937s, however. Very cool that you have two of them there, even if the condition is poor.