[JuliantheUnknown]

I hate to do this especially as this is my first post to the forums and site. However, I can

[The Australian Panther]

JuliantheUnknown, I'm not on staff but I think I can give you an answer. We try to make sure everything here is PD, but that is probably an impossible job, particularly when, as you point out, things that are PD are constantly getting renewed.

which would have meant both were impacted by the 1976 and then 1998 copyright extension acts meaning both should still be in copyright.

Also, we live in a time,  re cultural artifacts, like books, magazines, comics and music, where companies are bought up by new companies who then ransack the properties to see what they can reprint or renew. Also, now that Superheroes Movies are seen as a license to print money, [and Science Fiction properties] there are people scouring those for ideas and copyrights they can use. There are also no magic wands to efficiently find out what has come back into copyright at any given time. If approached by lawyers requesting that such and such a title is taken down, CB+ will comply. CB+ is also non-profit so theres no financial gain involved by CB+, which helps I would think. l There are probably other properties on the site whose provenance has changed. Its also complicates things that the laws can be different in different countries. So, British Commonwealth and US properties are mostly under the same laws, Europe under another and Canada under another. And if you are big enough, like the Mouse's company, you can change the rules.
Ironically, there are individuals out there who have taken advantage of the fact that most of what you will see on this site is PD to republish them to make money out of them. Easy Money, they think.   
CB+ is here, it survives, hell, it more than survives, its still growing and those who put the work and energy into it do what they can and should be commended for it.
Oh, and good first post and Welcome. Looking forward to hearing more from you.
Cheers!     

[SuperScrounge]

I have a vague memory of a thread, possibly here or on DCM, that while the information on the original term of copyright is easy to find, the government records on renewals less so.

There was some comment, possibly tongue in cheek, about marking a renewal with an R in pencil on the original form and renewal cards getting lost behind file cabinets.

If true that would explain why something would seem to be PD until a rights holder (with their own copy of the renewal form) has to complain.

[JuliantheUnknown]

Ah thank you for the explanation. And apologies for the late response - my router decided to die leaving me without internet for several days.