Interesting question. I just picked up a Zeiss Ikon Contina off of e-bay. Just my luck, it's also stuck. I haven't pulled it apart yet, but I have faith in my own abilities. Is the original spring still there or has it gone missing? If I can get mine open (I hope), I can mic the spring diameter, and give you an idea how to bend one for yourself. My verniers are at work for this week though. It may take me a while to get this one open. I'll need some time to figure this out. You ever pull the lens and shutter assembly out of your's?