I decided to take a chance and purchased this backpack at the flea market today for $25.00. There is a rectangular faded stamp and a smaller really faded oval stamp on the inside flap of this backpack. Can anyone tell me if this is an original ARVN pack?

you have a NVA or PAVN rucksack, i'm not going to venture a guess on its vintage though, so i'm saying it could be from 1960-2007. usually real wartime ones have a rubberized material type "sweat shield", but i cant tell what type of material is used on the one on the ruck.

I agree with lebelmilitaria 100%. Definitely NVA or PAVN pack.

There is a canvas rucksack that is similar to the US issue tropical rucksack that was used by ARVN troops. It had a metal "X" frame in the back. Those were all over the place in unissued condition in the 1970's, then got rare and expensive for a while, and recently I've seen them all over the place again,

The US ruck has three front pockets, the ARVN one two pockets.