@johnnyrod, the butkus manual says:
"Diameter of the super solinette lens mount is 30mm".
I used this info some weeks ago to get a skylight filter and lens hood.
But 30mm threads aren't small enough to screw in and not big enough to slip onto the lens.
I then got a 28mm filter to try and it seemed small enough, but it wouldn't screw in properly, as if the thread is a different pitch.
@charjohncarter and Ranchu, I've had it CLA'd. The assistant in the shop took it into a room and checked the bellows for leaks, and he said there weren't any, but I imagine another check was made by the technician who did the CLA.
@Scrambler, I found out myself about this 'outside diameter size' marking silliness, when I looked at the screw-in Agfa UV filter marked '37mm', and the slip-on Agfa Yellow-Green filter also marked '37mm' which came with an Agfa Ambi Silette which I bought last friday.