For your consideration are 2-quart canteens dated 1968 and manufactured by Hedwin. These are the most common versions available and are notable for their external seams and their relatively smooth texture.
Both canteens hold water and are free of leaks and holes. I have two available. One is unmarked and the other was marked by a soldier.
The collapsible 2-quart canteen was a leap forward in water carriage and a beloved piece of gear for over 40 years. No longer did soldiers have to carry multiple canteens to deal with the tropical heat. Advancements in plastics following WWII permitted the creation of pliable, yet durable bladders that weighed less than a single canteen. After multiple unsatisfactory iterations, the U.S. Military perfected the 2-quart canteen in 1967 and started to issue the canteens in large quantities in Vietnam.