Philippe
The date of production of the ZKK series is a 2 digit number on the left hand side of the front of the receiver where the locking lugs would engage Eg '63'!
I hope yours has the peep sight - wonderful rifle the BRNO's

The latest type pads are with sorbothane with really takes the bite out of sharp recoil.
The days of the 'rubber' type ones are very much numbered now, a simple squeeze test will easily find which is which.

There is plenty of info about on the 460 Weatherby, best in my opinion if downloaded to 450 Rigby levels, search amongst the reloading archive here & see how you go.
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93x64mm