The 502's

Levi's 502s were made similar to the 501 jeans except that there was a zipper installed instead of a button fly.
Characteristics are:

-Zip Fly
-Black bartack stitching at the top rear corners of the pockets
-'scovill' or 'gripper' zipper
-Redline inseam
-Big or small E red tab

These will fetch anywhere from 30.00USD up on Ebay.  Expect at least 60.00USD for Big E types as it designates the jeans as produced before 1971.

A patch listing the style as 502-0117                                                               Note the white in the lower left on the hem.  This is the
                                                                                                                               'Redline' selvedge, although the faint redline that runs
                                                                                                                                through the white is often faded.  The white 'ears' of the
                                                                                                                                 fabric are dead giveaways for redlines.