WOWZA!!! You hit the Jackpot!!!!
The 500, 503 and 401 are very sought after vintage machines. The 500 is nicknamed Rocketeer. There is lots of info on the internet about them and you can probably get free manuals for all of them. I'll have to check to see if I have the links to the manual for the 500.
Join us over in the Vintage Sewing Machine Shop section. You will find it if you scroll down near the bottom of the main page--it's in the Virtual section or here is the link:
http://www.quiltingboard.com/virtual...jsp?vsnum=1013
Here is a couple of links to read about a couple of the machines that you got:
http://blog.sew-classic.com/2008/10/...ne-review.aspx
http://possumjimandelizabeth.com/xht..._sing500a.html