Hello, this is a beginner's question but I am having a hard time understanding some of the details on this webpage about shutters.

For example this table should be simple to understand:

dimensions in mm Copal 0 Copal 1 Copal 3
1/board mounting thread M32.5x0.5 M39x0.75 M61.0x0.75
2/flange ring diameter 34.6 41.6 64.0
3/board hole diameter 34.8 41.8 64.2
4/front lens cell thread M29.5x0.5 M40.0x0.75 M56.0x0.75
5/rear lens cell thread M29.5x0.5 M36.0x0.75 M56.0x0.75
6/front to rear cells flange 20.0 +-0.025 20.0+-0.025 28.6+-0.025
distance

I can understand most of this but what is the flange ring diameter? I can't seem to figure it out.

Also, I what is the difference between an ordinary shutter and a press shutter. Why are they better for multiple exposures? Is it just the additional shutter cocking step that is eliminated?

Finally, I have been leaving my bag in the boot of my car and it seems that a couple of my shutters are dragging at the slower speeds, about a 1/4 sec and more. Is this normal with cold temeratures? If I want a shutter adjusted for these speeds, how much should I expect to pay - any recomendations for such repairs would also be appreciated.

Thanks for any help,
Anupam