Many of the Swiss Army knives from Victorinox include a small key ring. It is about 12mm wide (1/2 inch) on larger knives, and 8mm wide (3/8 inch) on the smaller knives.
Early, vintage Swiss Army knives never included a key ring, but this feature seems to have been introduced in the 1970's or 80's. A few models had different names for versions with and without a key ring (for example, the Spartan with key ring and the Standard without). Knives distributed with company names or logos are sometimes produced without the key ring.
Uses: You can use the key ring to attach your pocket knife
to a couple of keys, to a larger key ring, or to just about anything else.
Some people remove the key ring, or even file off its support. Although handy, it does sometimes snag on the inside of pockets.