Yes, but - in US law, unregistered brands can be protected as "Unregistered Trade Marks" - which is what (TM) means in the US, with (R) for registered marks.On the other hand, I'm not a trademark (or any kind of) lawyer. But one could assume if it was a registered trademark in the US, it would be in the database of US trademarks maintained by the US government.
In the UK (TM) means a Registered Trade Mark, we have Passing Off law which functions similarly to US unregistered marks.
Basically what that means is that even if you don't use Chaosium's lone registered mark; if customers look at your product and think it comes from Chaosium or is licensed by them, you may have committed a tort. A disclaimer may be helpful.