NBHAA
National Bicycle History Archive of America
What you have there was once a 1953 Murray Fleet Line. Absolutely, positively. No guessing necessary.
• The fenders were originally chrome.
• The seat, pedals, grips and sprocket have been changed. The tank, rear reflector, headlight and reflectorized chain guard are missing.
• The "S" in your model number has absolutely nothing to do with Sears, Roebuck & Co. This is an internet myth– regardless of how many believe it.
• While some parts do interchange between Murray Fleet Line (two words) and Western Flyer X-53 (all years), these two different bicycles were not the same, despite similar looks. The chrome carrier tubes do not interchange. The frames are different. The rear fenders are not the same and will not interchange. And there are other differences.
• Mercury and Murray Fleet Lines were different again. And not all Mercury bicycles in this design were designated "Fleet Line."
• Murray Fleet Line bicycles changed from year to year, even though for some years those changes were very slight.
• Also, Murray-Ohio's copywriters didn't always pay attention and got confused. If you look on the photocopy literature shown earlier in this thread you will see where the logo on the chain guard clearly says "FLEET LINE" in two words, but the copy above it on the same page says "Fleetline." It would have cost a lot to fix the mistake so the company let it slide. So sometimes they wrote "Fleetline" in the literature and catalogues, but this was a mistake. They meant "Fleet Line." The mistake was made so many times that the company finally gave up later and combined the two words into one– even though they never wanted it that way.
Records for every classic-era Mercury and Murray bicycle (and every Western Flyer X-53) ever made still exist at National Bicycle History Archive of America (NBHAA.com).