Expanding Your Trademark

When one files a trademark, one files on identification of goods or services, you have a listing. If I am a company and I sell product A and I trademark product A and I now venture out and I want to now sell product B and there’s no real relationship between products A and B. Let’s say one’s our boat and the other’s a car. They’re both vehicles but they’re really not in the same marketplace and I file the trademark for cars. Would I need to file a separate follow-up trademark for boats? I would say yes because simply the two products aren’t related. However, if I started out with sports cars and I went to pickup trucks, would I really need another trademark? They’re both motor vehicles, they’re close enough.