NASHVILLE (AP) — Nashville’s sheriff says there’s proof that Johnny Cash was granted law enforcement authority four decades ago.

At the Johnny Cash Museum this week, Nashville Sheriff Daron Hall unveiled a blown-up image of the late musician’s September 1979 deputy sheriff commission card, issued by then-Davidson County Sheriff Fate Thomas, featuring Cash’s headshot, fingerprint and signature.

Hall says one of his photographers discovered the card in a box.

The card authorized Cash to “execute any and all processes that may come into his hands and to maintain the peace and dignity of the State, and arrest any and all persons violating the Criminal laws of the State of Tennessee.”

Hall says he doesn’t have evidence of what the deputy work entailed, but Cash believed in prison reform and criminal justice reform.