To say there is a lot of data out there about sample slabs is an understatement, but it's all but impossible to (easily) find. Below are a series of currated links.
Conder101's book was the first attempt at an organized list of slabbing companies including samples. The book is long out of print, and quite dated, but it's a valuable reference.
Pro tip: The ANA Library has a copy. Join the ANA and borrow the book from the library for the cost of postage.
Cam's site was the first attempt to pull together only sample slab information. He had samples from 19 companies (ACG, ANACS, BLANCHARD, Coinland, COMPUGRADE, DCGS, Global, HALLMARK, ICG, INGS, NGC, NTC, NuGrade, Numex, PCGS, PCI, SEGS, SGS, and TruGrade).
Because so many new discoveries have occured, several people have tried to create new or updated lists of Sample Slabs in order to help date which slab and label was used when. These are customarily called "Generations".
The PCGS Slab Taxonomy by Lakesammman (Tim Larsen) and the Sample Slab Taxonomy are hosted at forums.collectors.com (the PCGS message board). here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
here and at archive.org from October 2021: here.
John, 86Saab@protonmail.com, has published several Taxonomy on Google
PCGS Slabs by Generation (slide show): here.
Photographic History of NGC Slabs by Generation (slide show): here.
Photographic History Of ANACS Certificates & Slabs By Generation (slide show): here.
ANACS Problem Grade Slabs (slide show): here.
There is nothing like words from the people who buried the bodies.
One of the earliest lists and very difficult to find on the web, "ANACS certificate & holders history". John D has a .pdf copy here.
The History of the First Third-Party Coin Grading Service – ANACS at CoinWeek.
The NNP at Washington University in St. Louis exists to "the goal of which is to freely share a vast online store of both printed and virtual numismatic resources. Books, periodicals, ephemera, as well as online forums and auction offerings will be captured in one location, freely available, and searchable from anywhere in the world. With unprecedented knowledge at their disposal, collectors and researchers will gain greater appreciation for numismatic science and more clearly discern fact from fiction." (from the NNP about page).
One of the confusing things is that many documents at the NNP are actually hosted at the Internet Archive, archive.org.
Isaiah's book is both a catalog of a personal collection and additional samples added through observation at dealers tables and websites. Isaiah takes an expansive view of "samples", so there are many things in his book that appear nowhere else. The first edition was in 2017. The second edition, 2018, is available at the NNP/Archive.org: here, and archive.
Issues of the newsletter from #1, February 2015 to #32, June 2019 plus several slab sale lists are available through the NNP: here.