As to chads and EFOs, the chads as you show, have a slightly just greater than zero, "efo-ness" as you show them. My

and

were addressing the fact a certificate was requested. When the chad(s) get impressed into the paper leaving a dent or dent and chad(s) it is not as intended, thus an efo even noticeable when the chad is blown or falls off. Yes, a production issue, but to most a damaged (dented) stamp.
However debris which includes chads becomes note worthy when it interrupts printing and creates a white space or halo around a white space. While paper pieces (including chads) happen the rare finds are the insects and threads from a whipping rag which can be quite striking, and expensive.
https://www.efocc.org/Resources/Hot...AA_Cover.php see, Freak 53 for an image.
EDIT: While typing this out, rodgcam slipped in the same link I posted, in which you will not find the term "chad." Here is the EFOCC home link--
https://www.efocc.org/main.phpA personal favorite of many is debris, circular, which landed perfectly on the eye of a 1901 Ben Franklin giving him a monocle look on that eye after the debris fell off. [Freak 53 as well]
Yes the EFOCC is a worthy group to join for EFO information, including back issues on line. Some where in those back issues you will find monocled Ben. I have been a member of the EFO Collector's Club since the 1970s. There is an auction each issue and exhibit awards are given, just to name a few benefits. It would also welcome an article about your chads and their certificate.
All that said, EFOs are not for everyone. Even 'Errors' per the USA EFO term of art, only interest some folks due to the prices.
I have an error where one full step of production was completely missed on a strip of five sheet stamps, with the row above and below each with a partial version of the missing material. Now if this involved ink, it would be big money, but alas, it was the gum which was not applied [Error 28]. All 15 stamps together demonstrate the "no gum" error and verify it was not just soaked off. Just to balance that, the most expensive single US EFO is, no, not C3a [Error 10] the upside down Jenny airplane, but Scott #85A, the 1 cent Franklin Z-grill [Error 27].