Let me korrect a few things. It was not the German Imperial Army, it was the Army of the Kingdom of Wuerttemberg. And there it was: 6. Batterie,in the 2.Wuerttembergische Feldartillerie Regiment Nr. 29. The familyname is WELZ, "Fahr" is not an abbreviation of his first name, it means Fahrer = Driver.
This are so called "Reservisten-Bilder" or also "Zur Erinnerung an meine Dienstzeit" = rememberance of my time of duty.They where made by the thousands. One background was used over and over again, just the foto of the individual soldier was added. It would be interesting finding family members of the Welz and Gutmüller Families.
The other soldiers familyname is GUTMÜLLER (Gutmueller), first name not known.The word Han is wrong ist must be Kan. and is an abbreviation of Kanonier and means gunner. He was a member of the 6. Battery, 4. Badisch Feld Artillery Regiment Nr. 66. That regiment was stationed around Lahr/Baden.