I am fortunate in that all my old Rapax shutters are consistently off. For instance, the 1/25th sec on the 162mm Raptar is realy 1/30th sec. Some speeds like 1/50th are dead on, but all old shutters are not alike. Some are flaky, and not consistent in any way. I would advise a test to find what speeds any old shutter is firing at. A CLA would not hurt, but will run about $80.