I have several of these machines and have sold two. This machine is said to be one of the best Singer machines ever
built along with the 500. It is all metal gears, direct gear motor drive, and a slant needle. It is tough and will sew
through anything.
Once they are cleaned up and adjusted you can fetch up to $300.00 for one. I sold both of mine for over $150.00
without the case. An original case in as good of shape as this one can add $90 to $100.00. An original plastic
attachment case and book can add another $50.00.
Craigslist is a poor place to sell good machines. Etsy is a better online site and you get a truer value for your machine.
A better place is in person at bazaars, home-shows, quilt functions, and local adds. You can sometimes buy them cheap but by the time you clean them up and add the case, book, and attachments there is a lot of value in the machine.
People who know the 401, 403, 500, and 503 appreciate them.