Some versions of the original Wenger Alpine Backpacker Swiss Army knife came with a blade lock. This model includes a thumb lever to release the blade when you are done with. The locking blade is much safer, since it won't spring closed by accident when you are using it.

Alpine Backpacker-- plain blade
Alpine Backpacker Serrated-- serrated blade
Backpacker II-- small blade instead of nail file
Camper-- adds toothpick and tweezers
Commander-- no scissors
Outback-- phillips screwdriver instead of corkscrew

Camper-- small blade instead of nail file, adds toothpick and tweezers