i do IP litigation for a living - apologize for what is going to be a bit of an info-dump (and for the many “it depends” hedged conclusions in here, but that’s the law for you): this has elements of truth, but it isn’t this clear cut and there’s no way completely eliminate the risk of legal action by the rightsholder:
(1) you are correct that the copyright is most robust over the renderings of the characters fixed in a tangible medium (so the pins/stickers), but it isn’t the case that any other depiction of the characters necessarily wouldn’t be protected — title 17 section 106 sub 2 extends the copyright holder’s exclusive rights to “prepare derivative works based on the copyrighted work.” this is a major backdoor for the rights holders to “control” works that they did not create (but that are closely based on their original authorship). it isn’t a bright-line standard, but if you started creating original mickey mouse episodes, for example, i can promise you that disney will sue you for copyright infringement (among other things) on a derivative works theory. (you’d argue fair use; even if you persuaded the court of that - it is a completely capricious doctrine, so there’s very little guarantee there; that’s why, for example, you ain’t getting e&o insurnace without an opinion letter from a lawyer saying it’s fair use - a fair use defense is going to be expensive to prove).
at a minimum, there would be a non-frivolous 106(2) claim that you’d have to pay to defend. if there’s serious money involved for the rights holder, you are a small player, and they are big enough (unlikely here), they will just grind you out through litigation costs.
(1A) that said, fixation may not be enough to create a copyright by operation of law in this case. the stickers are stamped 1981 i believe - that’s pre-US signing on to and implementing as federal law the berne convention, which did away with a strictly formalist registration regime in favor of the automatic-rights-on-fixation that we now (mostly) use — under the pre-berne regime, it wasn’t enough to fix the work, you also had to register it with the CR office, provide notice on the work, and deposit a sample with the CR office, among other formalities. if you didn’t, no copyright. the rest of the world has used the automatic-rights-on-fixation regime for a long long time, on the other hand.
sooooo if geedis/ta it was originally a US work, then based on its age, the lack of apparent registration with the CR office (based on my quick review, they never reg’d anything) might mean it entered the public domain and there are no copyrights to worry about.
(2) there may be (or have been, i agree there is a good abandonment argument), trademark protection as well, but it isn’t really a classic trademark claim because the characters aren’t being used to identify the source of goods/services such that the accused infringer’s use is likely to cause consumer confusion as to source of the work. (this is the basic framework of a trademark infringement claim). with famous characters like mickey who have taken on a secondary-brand ID’ing function for the consuming public, the character is more likely to be treated as a trademark even if not affixed to goods/services as a source identifier like your classic case. and if the characters are being used as a source identifier (like the trix rabbit, for example, who is directly connected to ID’ing a particular cereal source), it would be treated as a trademark too.
here’s my guess for why you regard it as a “trademark” issue, though: the Lanham Act contains the federal trademark law, broadly discussed about; it also contains what is known as a “Lanham Act section 43a” claim, which allows a suit based on false endorsements or advertising.” that is, if i create the false impression that the creator of geedis *endorses my goods/services (like my t-shirts with the characters or whatever), then even if what we are discussing is not technically a trademark, you could have a claim under the Lanham Act.
so while i’d probably at least plead a trademark claim as a plaintiff under the circumstances (because why not), i think other parts of the Lanham Act that are not technically about TMs like Sec. 43 would be the better claim.
anyway: i think this is very likely an “orphan work” — to the extent any IP rights do exist (see discussion of copyright formalities at time of creation above), i sincerely doubt the rightsholder is aware of those rights, much less actively policing and enforcing them. so you’d probably be ok.
but it is important to be aware that there would be real risks to deciding to proceed - you could easily get dragged into a lawsuit with enough merit to be very expensive even if it turns out that in the end that you win the suit. anyway: sorry for the super-long (and i’m sure only semi-coherent; rapped out on mobile in back of moving cab) comment. just wanted to clarify/caution re the risks involved.