This is a nifty vintage popover lightweight denim or chambray shirt from the 60s. Made by Continental Casuals, it's blue cotton with a white zipper opening part way down the center front. Short sleeves and pointed collar. Nice vintage shirt that doesn't want to be fussed over... easy to wear, easy care!
 
Pre-owned, used; in good overall condition. I just realized that there's a small frayed hole near the back hem... I'll take care of that later with some careful same-color mending. :-)
 
Marked as size M with 15" neck. PLEASE READ the actual shirt measurements-
Pit to pit- 21" across the front
Center front length- 23 1/2"
Short sleeve length- 9 1/2"
Hem- 45" around