after i remove the slotted screw, there is a recessed white non-metalic ring with a hole in the center through which the threads on the slotted screw pass. this white ring blocks the battery contacts which are not visible. i do not know how to remove this white thing. the method for changing the compass battery on the os 54 1 is extremely simple,i.e., take out the slotted screw and put in both batteries with positive side up. your help is much apprecisted sam costanzo phx,az