I wouldn't call them "Rare", but I will go as far as saying, that there were quite a few less 5 window COE's than 3 window COE's. I've owned close to 30 of them, & only 3 of them, were 5 window cabs. I've noticed most of the time, if it was a 5 window cab COE, it was either a Roadtractor to start out, or it was usually a '47-'49 model. I had a '48 Chevy COE 5 window, a '49, or '50 Chevy COE 5 window, & the '52 GMC 5 window, that I have out back. all the rest, I've had were 3 window cabs.