When I worked in an LCS years back Isabellas occasionally turned up mixed in with random foreign coins. Never with other ordinary quarters - that was for circulated commemorative halves. Some of them were relatively common to find mixed with ordinary coins: both Columbians, Stone Mountain, Cleveland, BTW, C/W, Oregon, both Pilgrims,(1934 mostly)Texas, Sesqui, Monroe, both San Diegos and more.