I did fix those key tops. Turns out that the 30's and 40's Smith-Coronas did not have celluloid or glass on the key tops. Instead, the letter for each key is printed on some sort of vinyl-like plastic. Fortunately, the keys from the Speedline were a perfect match for the Standard.
Also, please excuse the typos in my typecast. I guess that's what comes from excitedly typing on a park bench. In any event, the image has been scanned and there's no going back.