Victorinox SwissCard Blade
The SwissCard Lite includes a built-in magnifier which is slightly larger than the magnifier found on some Victorinox Swiss Army knives. Because the magnifier is built into the body of the SwissCard, it can lie flat against a printed page,or easily glide over a page.
This magnifier has about a 2x lens which is just over 1/2" (16 mm) in diameter. You can use it on insects, minerals, mosses, and just about anything else that looks better when larger.
If the sun is shining, you can also use the magnifier to start a fire. Just gather some dry tinder, and focus the sun's rays on the darkest spot in the tinder material.
The magnifier lens is made of plastic, so be careful not to scratch it. Some people wrap it in a small piece of plastic so it won't be stained or abraded by pocket crud. The SwissCard magnifier is particularly vulnerable to abrasion, since it isn't folded into the knife body like the one on regular Swiss Army knives.
Other Magnifiers
A number of Victorinox Swiss Army knives have the fold-out magnifier.
Some of the Wenger Swiss Army knives also include a magnifying glass, which is on a longer arm.
A few of the Victorinox Swiss Army knives come with a travel kit which also includes a combination ruler, compass and magnifying glass. That magnifier lens is larger (about 3/4", or 18 mm), and it's easier to keep clean and protected than this magnifier.