Since trademarks exist to tell consumers the source of goods, how can it be OK for two companies to use the same trademark?
Sometimes, using the same mark is NOT likely to lead to confusion:
- Consumers are unlikely to be confused if the companies are in different fields. No one thinks DOVE® soap and DOVE® chocolate come from the same company.
- Companies can also share a trademark geographically if they’re purely local. Tony’s Cleaners in Concord, NH is probably not the same as Tony’s Cleaners in Seattle, WA.
But what if two companies use:
- the same trademark
- for the same stuff
- in the same market?
We recently saw an example of this: co-ownership of the trademark SUPER HERO by Marvel and DC Comics.
Another example is SWISS ARMY, which was used for decades by both Victorinox AG and Wegner, S.A. That co-use was allowed because of some very specific circumstances:
Consumer confusion was not an issue because the quality was identical.
Wegner and Victorinox both made products to the specifications of the Swiss Army, so both products were of the same quality.
Consumers can know the source through other indicia. 
Victorinox pocketknives were sold as THE ORIGINAL SWISS ARMY KNIFE and Wegner’s were sold as THE GENUINE SWISS ARMY KNIFE. Each also used different versions of the Swiss cross on the knives:
If you think this is an extremely rare set of circumstances, you’re right. The rule that two companies can’t use the same trademark holds true, but there are occasional exceptions.
Big shout out to Bill, for suggesting this topic! What do you want to know about?
 In 2005 Victorinox acquired Wegner, so the issue is no more.
 We saw this with SUPER HERO, too. Both Marvel and DC tended to use their “house brands” together with SUPER HERO.