After some SAK "hunting" on the internet, I've noticed that the same model has two ID numbers. Let's take the Classic silver Alox for example;

On the official website the ID is 0.6221.26 .
http://www.victorinox.com/ch/product/Swiss-Army-Knives/Category/Classic/Classic-Range-58-mm/Classic-Alox/0.6221.26

However, many online stores ( eg.
http://www.amazon.com/Victorinox-53012-Classic-Silver-Alox/dp/B004Y4QOI0
http://www.jacksonshardware.com/store/pc/viewPrd.asp?idproduct=6198&idcategory=177 )
show another ID - #53012 .

I'm confused. Why do they have different ID numbers? Is there a good reason for that, or are they trying to make SAK collecting harder for us ( like it isn't hard already  ) ?

The shorter stock numbers are the North American ones. Stuff is the same, check out Sakwiki.com, both stock numbers are up for every model.

Thought that could be it... That doesn't make much sense if both stock numbers the same, why wouldn't they use only one? I was planning to make a table for Vic SAKs to organise them, but now I have to do it with the European and N. American stock numbers. 

Thought that could be it... That doesn't make much sense if both stock numbers the same, why wouldn't they use only one? I was planning to make a table for Vic SAKs to organise them, but now I have to do it with the European and N. American stock numbers. 

That's definitely it, no maybe about it. Victorinox originally sold knives in countries outside of Switzerland via a distributor arrangement. The distributor in the US - R.H. Forschner - was a completely separate company. They bought Victorinox knives, created the advertising, stock numbers and marketing and sold them in the US. This is a pretty common arrangement for international companies. R.H. Forschner eventaully became SAB (Swiss Army Brands) and now, I think, is owned by Victorinox themselves (not 100% sure on that).

The difference in the model numbers is the difference between Victorinox's model numbers, common in Europe, and the Forschner/SAB numbers they made up for the US. European numbers are typically in the x.xxxx.xx format, and are actually a code that indicate what the knife is. SAB numbers are typically a 5 digit number starting with "5" that appear to be just sequential model numbers without any sort of code behind them.

http://swissarmyblogs.com/2011/06/victorinox-r-h-forschner-brands/

Also Victorinox has changed their numbering system several times over the years, so the same model can have different numbers depending on when it was made.

Names are an equally big mess. Victorinox regularly recycles names. Golfer has been used so often that it's a running joke that any new unknown model is assumed to be a Golfer until proven otherwise. Wenger's just as bad. They regularly use the same names as Victorinox; sometimes for similar models, sometimes for something completely different. All part of the fun.

The names can often be confusing, but, w/some rare exceptions, Vic's numbers can be very helpful in identyfing a knife. The numbers, & their placement in the series, indicate not only which tool are in a particular knife but also what color & material the scales are made of.
If you like solving puzzles, you can readily figure out what numbers equal what blades. It's not that difficult. Be aware, tho, some numbers indicate a combination of blades.

Here's the current (I believe) Victorinox numbering system.

http://www.bladeforums.com/forums/showthread.php/679187-Victorinox-Model-Numbering

Here's the current (I believe) Victorinox numbering system.

http://www.bladeforums.com/forums/showthread.php/679187-Victorinox-Model-Numbering

I'm afraid the chart is off - take the Rucksack and Minichamp for example:

Rucksack: 0.8863
0.- guess it's correct, not sure what size they are referring to.
88- not listed
6- the wood saw, metal saw/nail file, chisel and fine screwdriver are listed in the category 6. The rucksack only has the wood saw.
3- Correct.

Minichamp: 0.6385
0.- again, not sure what size they are referring to.
63- combination tool (?), corkscrew and mag glass with Philips screwdriver. The Minichamp has none of those.
8- wood saw, metal saw/nail file, chisel, fine screwdriver and fish scaler fall into this category - Minichamp has only the nail file.
5- no pin

I can't find a Victorinox numbering system that's actually correct 

Here's a 2006 Victorinox catalog with a partial numbering system on page 3.

http://www.sosakonline.com/images/stories/Catalogue/March09/Victorinox%202006%20complete%20Catalog.pdf