According to one IP Lawyer and scholar, trademarks on public domain works are not as strong as people might think. It must not only refer to the product, but carry a secondary association to the trademark holder. Disney doesn't have to worry too much about Mickey Mouse, the Cinderella castle or even their version of Tinkerbell due to the fact that the average person automatically associates those with Disney. So, even when those fall into the public domain, they still have strong copyright protection. Superman, Archie Andrews are other such strong trademarks (in fact the earliest stories of Archie are public domain now). However, most public domain works don't have that secondary association, such as MLJ/Archie's Steel Sterling. So, I think any trademarks regarding Miss Masque would probably have to be to specific product in order to not have similarly named products on the shelf at the same time (such as competing comics from different companies), but not a trademark on her in general. A caveat though, according to him, he could only find one case that directly addressed the issue, so it's not something with a lot of decided rulings behind it.
http://copyright.nova.edu/mickey-public-domain/I will also point out just in general, not all of Nedor is public domain. Many of the first couple of issues of various issues of their comics and some of their pulp line was registered and renewed. However, they do seem to fall under "orphan works" because the characters are widely used by various companies and the comics reprinted without a hint of problems. It is possible that over time with the various break ups and sales of the company and its various publishing properties, the rights to the comic characters were lost along the way.
