Help ID these pants please (early ERDL?)

[blademan]

A friend just gave these pants to me. They were issued to him. They appear to be non rip stop poplin, talon zipper, exposed buttons on pockets and top of zipper, all pockets are sewn to outside of pants.  No tags or markings other than my friends name. I believe he was a medic in the VN war. I believe them to be early viet nam erdl. Can anyone help me with this ID and relative value? 

Thanks

[kammo-man]

Army surplus pattern 

owen 

[blademan]

1 hour ago, kammo-man said:

Army surplus pattern 

owen 

Thanks for much for the info. New to this era of clothing.