Not once, but twice... I got two shutters sight unseen. "Oh yeah, these are Copal 3 shutters."
Some of the 3S shutters are marked as 3. I have two of them. Both work fine, but only one has a retaining ring.
I offer them both for a single Copal 3 in good working order. Must have retaining ring or flange. I get to keep my blank iris scale.