The PRINCE experts think this could be his earliest known concert shirt. He was on his 1st ever tour and was playing smaller clubs. Tour started Nov 5 1979. The concert on the shirt was a 1-off show in Nashville with only 7 previous concerts before this date.
(Please note: Legit checks I do in this forum should not be considered 100% conclusive; I'm simply giving a gut reaction based on the limited information provided.)