The Wenger packlock mechanism is a very interesting part and it got variations in history. Our date on this is from 1979 and in catalogues from this year there are many
knives with this lock.
I would not be surprised if it is a Wenger invention from 1977 and please feel free to share information if you have inputs.
This lock is only made for the purpose of preventing accidental closing and it is a safety feature for normal use. The release button is easy to see and one only needs to press it down and move the blade into the body
of the knife. When the lock is released and blade is in the body the lock serves no purpose. The blade is also held in and out by the spring like usual; the lock is only active in out position.
It is normal that one can move the release button up and down some when the blade is in and out.
On the picture you can see part of the tang on a knife to the left, this is
on a wenger knife I have been researching and it got very high precision because there is an extra step, if it is better I do not know.
The packlock is a very incredible invention because
it requires miniature precision on an 85mm knife. It is not easy. Only imagine the precision one need to make a normal Swiss Army Knife and now one get the additional parts and locking. And this was done in the late 70s! To make the spring fit into the "tang"
part of the blade requires precision. The release button is pressed down to lift the spring out so one may fold the blade in.