Wenger packlock 1 13 51 ?

[North Man]

Hi
Here is a good question, on the pictures you can see two of them. I found them listed with 1.13.51 European numbered.
 This model is well known. The knife on the right is from around 1980, then the one on the left got a different shape at the tang, it functions very well with the locking mechanism. Tight and well.

We know the packlock was introduced around 1977 approx. We also know that on the late 70s approx we get a thinner tang on the corkscrew and loop different. The right knife is thinner than the late 70s corkscrew but just some thicker than the left knife( with the different tang for locking)
The function and Lock operates the same.

 I am not sure to date this and why it got a different tang(knife blade locking). (before or after 1980) It got no function standing in any position, i mean a half stop for show purpose. It is for the locking only

[North Man]

pic, left knife got slightly thinner and shorter tang for corkscrew

[basilio]

Nice knives!
This model is listed in the wiki as a variant of the Alpine Backpacker.
As for your question, I don't know.
There were a lot of changes on the tools, and sometimes you happen to notice them only when comparing, side by side, two models.
For example, I only noticed when taking the picture shown here (reply #1114, second picture attached)
http://forum.multitool.org/index.php/topic,32456.1110.html
that on the newer models the metal saw not only does not have the nail nicks, but it is actually longer by few mm.

[North Man]

Yes you are right

[North Man]

I put in another picture of the different tang part (for the spring with locking mechanism). Where the tip of the toothpick it goes up a step( this mean two raised parts). Very different than the normal one..