Those are later Amos. ANACS was originally owned by the ANA (American Numismatic Association) and used the smaller SWH (Small White Holders). There are a lot of stories, the public one from the ANA board is that they didn't feel it was appropriate as a non-profit org to put the million dollars it would have required for modernization into a for-profit enterprise. And so ANACS was sold to Amos Press (Coin World). Amos chugged along with the SWH, and converted from the two-letter/four-number serials to all numeric. Then they introduced the larger SWH. Finally, ANACS was sold to Anderson Press (owner of Whitman Publishing, e.g. the Red Book). Anderson introduced the curve-top slab used today, and the blue labels. The highest SWH cert number is just over 3,000,000 so your 2.7m is towards the end of Amos. Your 1.2m is late-middle. Why does any of this matter? Well... ANA ownership was technical grading as described in the Official ANA Grading Standards. Under Amos, grading moved more towards the "market grading" that everybody uses today.
I would search Great Collections for these but they really seem to have a premium on silver dollars the last year or so . Still get one now and then
People think that because they are old, they will upgrade. Maybe and maybe not. The ones that have been in the market for years have been looked at many times and probably will not. Fresh material is more likely to upgrade or cross at grade.
I have a few. Wizard sells boxes that fit these slabs if you're interested. Photo is of mine. https://www.wizardcoinsupply.com/product/intercept-shield-anacs-track-box.html
I love the little soap bars. Here are some of mine: I have others but I'm missing the slab shots for them.
There was another company that used to make boxes for these called Eagle. I found an example currently on eBay (not my listing-image copied from link). https://www.ebay.com/itm/266838844551
I like these slabs as well (and have noticed the differences between generations like Burton pointed out). Below we have two Gen 4 (1991-1996) slabs and the grades are fair (not premium or under graded but fairly accurate in my opinion).
Some people liked the size of these holders because more of them could be stored in limited spaces, like safe deposit boxes. The only downside for the ANACS company was that they were too small to hold a $50 gold piece, like the two Pan-Pac coins. Of course demand for grading those would have been limited, given their small numbers, but it was a minor disadvantage.
I have sent a lot of these holders to Great Collections. My thought was to have PCGS crack them and grade them. GC talked me out of it. There seems to be a nice following of these from collectors. They were correct and most of them brought nice prices at auction. I made good money and saved a lot on grading fees.
Here is by far the most valuable coin I have in an ANACS "soap bar" slab. This is minor type coin in the U.S. gold series, and it's quite scarce. Maybe I was stupid to buy it, but it is a decent example of the type. This was Christian Gobrecht's early design for the $10 Liberty gold piece.