The machine pictured on ebay looks just like mine that is from the late 40s / early 50s. (Don't remember which of my machines, the featherweight or the 15K, is from 1949 and which from 1953).

I would buy it because it is clearly a featherweight. If you just want it for your own pleasure it doesnt matter what the serial number is just enjoy it. I have a black 1951 and a white 1964 and they are both great.