If it's a 111W, it is a compound feed machine (a combination of needle feed and drop feed) with alternating presser feet , which is another way of saying walking foot. The 151 designation must mean it is a special machine made for the government, 'cuz there's no mention of that particular model from Singer. I don't know why it uses the 211W feet, but that's what you'll need to get. It's also odd that the machine would be a "W", 'cuz that means it was manufactured in Germany which makes no sense if it was during WWII. Do you have the serial number?
No one lives forever, the trick is creating something that will.