Ok understood.
Again, the -A- is either an inspectors mark (which Walther never used on mags) OR it's the ID mark of a contract company that made the mags for Walther.
Many, if not most gun companies don't make their own mags, they contract them out to companies like Mec-Gar.
In the past, the Walther/InterArms guns magazines had NO such mark. Now that the guns are being made by another company for S&W, they may be adding an ID mark.
If this is a recent gun, look for contact info in the manual, and call or write them for spare mag sources.
As a matter if interest: Did the mag you bought later come in a Walther package, or does it have the Walther banner on it?
If not, it's almost certainly not a genuine Walther, and that's why it isn't reliable. A lot of people are complaining about after market mags for the PPK/s that don't work well.