Here's what I know: There are two main styles of watch case openers - those in the 84mm "student knife" frame (Pocket Pal, Secretary, etc) and those in the 84mm "Officer's Knife" frame (Bantam, Cadet, etc). Student FrameIn the 84mm student knife frame there are variants in the scale type, the design of the watch opener tool, and the tang stamps. In scale material, the vast majority are made in smooth alox that look like a Secretary (like the one shown in this thread). There are also variants with cellidor scales like a Pocket Pal and checkered alox like a Popular. The Secretary and Popular styles are always some sort of advertising knife, typically for a watch company (Breitling, Omega, Rolex, etc). I imagine that one aspect of collecting these would be to get different versions based on the companies that are being advertised, much like the way many people collect different types of Classics.For the design of the watch opener tool, again most look like the one shown in this thread, but a few show up with a notch in the opener part (see attached). Not sure if this is a mod someone made to the tool or not, but it does show up on several knives from many different sellers. Finally, for there are many tang stamps found for this variant -- the main ones I've seen are (f/r):VxSS/VictoriaElinox/VxSSRVxSSR/-Officer's Knife frameIt appears that sometime in the late 1990s Victorinox stopped making the student frame type watch case opener and switched to a 84mm Officer's Knife type - basically a Bantam with watch case opener blade. Approx 40% of the time this type has regular eco scales without ads, and 60% of the time they do have ads on them (either screen printed on the eco scales or inlaid on regular cellidor scales).