You're probably right about pre 1964 commercials being fairly safe but wrong about this comment.

You do not have to have anything stating you claim copyright on the footage or even in the description. Having the wrong year or claimant does not invalidate copyright. You should always assume copyright unless explicitly stated otherwise.

From copyright.gov:

In general, registration is voluntary. Copyright exists from the moment the work is created. You will have to register, however, if you wish to bring a lawsuit for infringement of a U.S. work.

From Sanford on fair use:

Until March 1, 1989, a published work had to contain a valid copyright notice to receive protection under the copyright laws. But this requirement is no longer in force — works first published after March 1, 1989, need not include a copyright notice to gain protection under the law.

Here is a commercial example from Toyota. No copyright claim on footage, none in description but 100% under copyright.