Yes, I think opening these shutters should be left to the experts who, I understand use ultrasonic cleaning.

This thread motivated me today to measure the shutter on my new-to-me Century 2x3 with the Wollensak Syncromatic C / Graftar 1/4.5 103mm
{ speed, ideal, measured millisecond}
{1/10, 100, 95}, {1/25, 40, 40}, {1/50, 20, 25}, {1/100, 10, 15}, {1/200, 5, 5}

Below is a trace of the 1/50 measurement showing how I use the mid-point of the rise and fall times - (shutter is halfway to maximum transmission)
I don't know how they measured them back in the day.
The ripple on top is 120 Hz ( 8.33 millisecond) from the test lamp I use. I should put a rectifier filter, however it allows a useful cross check of the time, in this case 8.33 ms by about 3 cycles.