It is challenging to identify any Swiss army knife (SAK) as they all share the same appearance and basic functions. It is even more of a challenge to to so from a photo on iNaturalist, where a knife would be used to provide a reference scale rather than the main focus. But it can be done! Here are some models I have managed to identify from observation photos:

Victorinox 91 mm models

• Climber: https://www.inaturalist.org/observations/193914223
  It differs from the Spartan by the addition of a third layer which contains scissors and a multipurpose hook.

• Compact: https://www.inaturalist.org/observations/185964632
  The Compact is the same size as a Spartan or Tinker, but replaces the layer containing the can opener, cap lifter, and awl with the scissors and a specialty multipurpose hook with an integrated nail file. It also replaces the small blade with the combo tool (can opener, cap lifter, wire bender, flathead screwdriver). The Compact is also one of the few models to come stock with plus scales, which include a slim ballpoint pen. This particular knife is one of my own personal knives, customized with black scales and red scale tools.

• Deluxe Tinker: https://www.inaturalist.org/observations/194605349
  It includes a third layer with pliers. It is easy to spot, even from the spine, because of how thick the layer is.

• Elinox Standard: https://www.inaturalist.org/observations/140303732
  Elinox models had a different style shield. Certain manufacturing steps were changed or skipped to produce the same quality knife at a lower price point (such as hot foil-stamped logos instead of steel inserts, and tools that were not polished). They often did not include the tweezers and toothpick. The Standard is otherwise identical to the Spartan.

• Fieldmaster: https://www.inaturalist.org/observations/197018717
  It is similar to the Huntsman, but replaces the corkscrew with a Philips screwdriver. I was able to confirm from another observation: https://www.inaturalist.org/observations/196969358

• Ranger: https://www.inaturalist.org/observations/163730471
  This adds the scissors/multipurpose hook, the wood saw/small screwdriver, and the metal file & saw/chisel to the Spartan toolset. I carry this same model every day and really quite like it. It has one of the highest tool densities for its size—to get any more tools you would need to upgrade to the SwissChamp. Here is another angle of the same model: https://www.inaturalist.org/observations/307875

• Spartan: https://www.inaturalist.org/observations/211937957
  The Spartan is the base model for all 91 mm Victorinox SAKs. It has two layers of tools: the large and small blade with a corkscrew on the spine; and can opener/slim Philips and cap lifter/large flathead/wire bender with awl/reamer on the spine. Other models add or replace various tools. There are other sizes which I'll describe below. The particular SAK featuring in the above observation has black instead of the archetypal red scales. Many colors are available from the factory for most models, and they are also easy to customize yourself.

• TimeKeeper: https://www.inaturalist.org/observations/103373522?photo_id=172993899
  This is a pretty rare model, which has an analog watch in the scale. It otherwise has the same toolset as the Compact.

• Tinker: https://www.inaturalist.org/observations/179581874
  The Tinker is a sub-base model, differing from the Spartan by replacing the corkscrew with a Philips screwdriver. Many models derive from the Tinker as well. Here is another Tinker which has been customized with Swiss Bianco aluminum scales (by yours truly): https://www.inaturalist.org/observations/191025667

• Traveller or possibly others: https://www.inaturalist.org/observations/41942217
  This has the same tools as the Climber, and includes a digital display unit built into the shield-side scale. It features a clock, altimeter, barometer, countdown timer, stopwatch, and thermometer. The display is not visible in the above observation, but you can still identify it because it has the extra slot in the reverse scale for the tweezers (which would normally be on the other side). Aside from the Traveller, this model may actually be the Traveller Lite (which adds in-line Philips and a flashlight), the Altimeter or Altimeter Lite, or the Expedition/Expedition Lite. I can't be certain from the available photo.

• Super Tinker: https://www.inaturalist.org/observations/199251387
  It differs from the Tinker by the addition of a third layer which contains scissors and a multipurpose hook. It is also similar to the Climber but replaces the corkscrew with a Philips screwdriver.

Victorinox 84 mm models

• Ecoline Bantam: https://www.inaturalist.org/observations/209213317
  The Bantam has a single large blade and a combo tool. Newer Ecoline models have nylon scales which have a frosted, matte finish and a silk screened emblem. This particular knife is a promotional model with a custom printing.

Victorinox 111 mm models

• Hunter: https://www.inaturalist.org/observations/231668325
  The 111 mm models are significantly larger tools, with contoured handles and locking main blades. This example has a slide lock in the back scale but after 2017 all 111 mm models were updated with liner locks. The Hunter is usually offered in Victorinox red, but an olive green version is also available. There are some special editions in olive green but I don't think this is one of those.

Victorinox 58 mm models

• Classic SD: https://www.inaturalist.org/observations/205126067
  This is a short model (58 mm in length) and small enough to fit on a keychain. It can be distinguished from the standard Classic because it features a screwdriver tip on the nail file (SD = screwdriver). Another Classic SD in blue: https://www.inaturalist.org/observations/200864951

• MiniChamp: https://www.inaturalist.org/observations/236108657
  The MiniChamp is loaded with nearly all the tools available in the 58 mm line.

• Rally: https://www.inaturalist.org/observations/197585103
  This is another 58 mm model based on the Classic, which replaces the scissors with a combo tool (Philips screwdriver, cap lifter, and wire bender).

I do not recall coming across any Wenger models here, but I plan to keep updating this journal post. I stand corrected!

Wenger

• Commander probably: https://www.inaturalist.org/observations/214711681
  It appears to be a two-layer knife, but the tools are not very visible so I can't narrow it down much. My guess is that this is a Commander, which is the base model of the Wenger 85 mm line. It could also be the Canyon, Highlander, Trailblazer, Viking, something with 3 or 4 layers, or any model featuring tools on the spine and an cutout in the scale to access the nail nick. All Wenger models have been discontinued for a decade (except ones that live on as Victorinox Evolution and Delémont models, which feature some of the same toolsets) so this is an especially uncommon SAK to see on iNaturalist!

Unbranded

There are countless examples of unbranded knives, or variously branded, but are not made by Victorinox or Wenger. I will attempt to list a few examples. By nature of these brands I do not have model names for them (if you know, chime in please!)

• Q: https://www.inaturalist.org/observations/99006667?photo_id=165627815
• Metal Scales & Plastic Texture: https://www.inaturalist.org/observations/220135012

• Metal Scales: https://www.inaturalist.org/observations/97407457
  This one has a flashlight!

Honorable Mentions

• Victorinox Compass Tool: https://www.inaturalist.org/observations/10451278
  This tool—a combination compass, thermometer, spirit level, magnifying glass, and ruler—was available paired with the Expedition Lite as part of the Expedition Kit, or as part of the SOS Kit which included the SwissChamp and a number of additional accessories. Here is another view through the magnifying lens: https://www.inaturalist.org/observations/10451508

• Victorinox SwissTool: https://www.inaturalist.org/observations/68958148
  This is a very capable tool made by Victorinox but it is firmly a part of the multitool family rather than a traditional Swiss army knife. If I were to include it in the project, I would feel compelled to include all Leatherman, SOG, and Gerber multitools as well.

• Victorinox Swiss Classic Paring Knife: https://www.inaturalist.org/observations/194491440
  This perennial utility knife is found in the kitchen, the garden, in tackle boxes and aboard boats. It is inexpensive and always seems to be sharp. It is not a Swiss army knife, but made by the same company, and is worthy of a shout-out.

• Victorinox Belt Sheath: (placeholder; I lost the URL, but when I find this one again I'll add it).