Made in USA

I have just been given several paper shotgun shells and I noticed that on some of the headstamps it says “Made In The USA” and others not.At what point in time was this added?The following are the Mfgs.

   Winchester: Ranger, Reapeater
   Western: Super-x, Field,Xpert
   Peters: H V, Victor

I don’t collect these but would like to know about time of Mfg.

I don’t think many shotgun cartridges have the country of origin on the headstamp(?)