Hi Rino,

Agree with you about and like the original peep sight of the earlier ZKK series.

But I definitely don't like the Rigby style peep sight on the cocking piece of any bolt action rifle.
And this is because it increases the weight of the firing pin system, so it also increases the lock time. Not good to me.
Instead I would put a peep sight mounted in the CZ 550 mounting rail of the rear bridge.
Recknagel makes this peep sight. By the way, I have one in a Weaver type base in my FN Akah Mauser .30-06. And works very well!

The Recknagel link is:

https://www.recknagel.de/Joomla/images/stories/Downloads/Recknagel_Zubehoerkatalog_9_Internet.pdf
It is on page 7.

I bought mine through NECG (New England Custom Guns). I can recommend it.

Good luck!

PH