The Watch-Case Opener, or Case-Back knife, is designed for the horology industry. The special blade is used for opening watches with a pressure fit (snap-back) case.
Both Swiss Army Knife manufacturers have produced these special purpose blades for a long time.
Most models featuring this tool are advertising premiums made for various watch-makers and jewelers. Normally, these are small Alox scaled models, however, the tool is also found on the largest collector's versions of the Swiss Army Knife.

Victorinox

The early Victorinox versions are smaller, have a sharper edge, and come to more of a point. Later versions have a wider more rounded blade.

Victorinox Watch Case Opener	Different Victorinox Watch Case Openers

Wenger

The Wenger version tends to be larger, more rounded and with a more dull edge. However, over the years Wenger has made a number of different blade styles, as watchcases have evolved and changed in size. Wenger also makes another case-back-opener model, with a fixed-blade that does not fold into the handle of the knife. This model was in production until at least 2012.