REM are offering a reward for the return of guitarist Peter Buck's black Rickenbacker 360 guitar, which was stolen following a concert in Finland.
In a statement on their website, REM said it was taken from the stage after the gig in Helsinki on Tuesday 9 September.
Buck has used the guitar both live and in the studio since the band released their debut EP Chronic Town in 1982.
"Needless to say, this instrument means a great deal to Peter and to REM," the band statement read.
"It is our sincere hope that whoever is responsible for the loss, or whoever has information which can help recover the guitar, will come forward to receive a generous reward, no questions asked."
A few years back, Buck was asked what single guitar he would keep above all others: "It would be the Rickenbacker", he said. "I've been playing it since 1980, on every record we've ever made."
MusicRadar is not sure where the thief hopes to sell the guitar, really - although it's 'just' a stock 360 it would be recognisable to many guitar dealers.
Watch REM in 1983, playing Radio Free Europe.