Changed the light seals on the Mamiya RB67. The rotating back to body seal has never been changed before. Did Mamiya use glue made from bears teeth on those seals ? REALLY REALLY HARD TO SHIFT.. I know it is the original glue as I came across the very same stuff on C3 seals. This was on a camera that had not been used since 1970 seals had turned to powder. Glue hard as flint.