Correcting My Biggest Misconception
___
On my sources page, I made something very clear: "...nothing confidently touted should be radically changed. That means we did something wrong."
Well, today I found out I did something wrong.
As of the time of writing, I've been working on compiling information for the 702 Special Introductory Set, specifically trying to confirm the date of certain magazine scans.
I decided to check newspapers again, searching using some keywords used in the ad to try and pinpoint when exactly that featured version of the paragraph was written/used. In my search results, I came across a 1965 ad that I'd missed when I originally gathered my newspaper clippings because I previously only searched with "LEGO Samsonite":

Huh?
Why are two sets that are universally cited to have released in 1966 appearing in a late 1965 newspaper? I initially collected it to add it to my article on newspaper mistakes, as I assumed it to be an accidental 1965 use of photos intended for the 1966.
Until I found another from 1965. And another, and another, and another. I found different hundreds of toy stores across the United States all using different images of sets thought to have released in 1966... could they all have accidentally used the wrong pictures? How did I miss this?
First, let's address why I previously assumed that sets like the 205 Basic Set and 042 Jumbo Brick Pull-Toy released in 1966.
Department Store Catalogs as a Source
In the past, major department store catalogs have been the major source while piecing together LEGO Samsonite's history, as it has been assumed that any new sets would first appear in those catalogs before any else.
For example, this 1965 Eaton's Christmas catalog features the 1961-65(1966 for Canada) lineup, even missing the 001 Gears and 002 Motor Pak set:

Or this 1965 Spiegel Christmas catalog, with the 705 Basic Set, 708 Basic Set, 711 Basic Set, 001 Gears, and 002 Motor Pak:

And this 1965 May Co. catalog(same as the 1965 Jordan Marsh catalog) features the same assortment of sets:

Even JC Penney's 1965 catalog still contained only previously existing sets:

Then in 1966, JC Penney's Christmas catalog updated to the new line of sets:

However, there is only one 1965 catalog that contains the 120, 003, 205, 285, 375, 450, and 615 sets. It is FAO Schwarz:

How is this possible? Why do all other catalogs not have the new wave of sets listed for Christmas in 1965? Why do some have the 001 and 002 sets, which were also new for 1965, but not the rest?
I'm ready to make the argument that the 001 Gears and the 002 Motor Pak were ready for the 1965 season a lot earlier than the rest of the sets. How do I know this? It's not a guess, the 695's pamphlet makes a very strong case:

Did you notice how the only sets that have completed box designs are the 001 and 002 sets? Given that, my argument is thus: because major department store catalogs like Sears were being released sometime between August and September(known via Wikipedia), they only advertised the sets that were available at the time of compilation(which would be as late as summer):

Of course, this raises a valid point: if massive department stores like Sears missed advertising the largest LEGO release in America up to that point, how was FAO Schwarz uniquely able to have the correct assortment advertised?
The difference would be in timing for catalog preparation and FAOs relative simplicity.
I have a lovely example from FAO Schwarz. In 1961, Samsonite did not start production of LEGO until October, known via The Toronto Star, August 4th, 1961.
However, the 1961 FAO Schwarz Christmas catalog shows a prototype version of the 708 Basic Set and the 717 Junior Constructor(along with a placeholder image of the European Town Plan they were using to represent the 725 Town Plan), which means that at some point before October was when the catalog was prepared.
So because it would appear that FAO Schwarz could've prepared their catalogs later than other stores(at least as far as I can show), that'd easily explain the discrepancies between the store catalogs. The previously assumed 1966 sets simply were available a lot later in the year and thus were missed from larger catalogs that required preparation earlier in the year.
It would also follow that since FAO catalogs are relatively simple(as more images are recycled from previous years than are new), it would just be a matter of changing text. The issue now is that we've confirmed the 120, 205, 285, 375, 450, and 615 sets were at least being advertised in 1965, which other ones can we confirm? Was it only FAO Schwarz?
Thankfully, via brickfetish, we have a dealer order form with a confirmable date(August 1965) that shows both the 1961-65 sets and the 1965+ sets for order at the same time.
Logically, it would make sense that the new wave was made available for Christmas of 1965. I don't imagine toy store owners in August wanting to order a new line of sets that wouldn't arrive until after Christmas, it wouldn't make sense. It does help to explain why stores like Sears might be missing those sets from their catalogs, as that order form is from August of 1965.
Those are some pretty solid ideas with good reasoning, but we still need to show that these sets were actually on shelves in 1965 in order to propose such a drastic revision. Otherwise, to tout a 1965 release would be a short-sighted theory.
Sure, we have the a catalog above, but I want definitive, unmistakable proof that the sets were widely available and not quietly released at a select few stores.
Were the 1965 sets available for a wide release?
How is it possible that Samsonite produced this new wave, expanding their line with more mainline sets than before? Their Detroit plant closed in 1964.
Thanks to this April 9th, 1965 article from The Daily News Journal, we know that Samsonite opened the Loveland plant in 1965 specifically for LEGO production. But that does not mean Samsonite of Canada could not have continued manufacturing parts for both countries, as remember, for 1961-64, Stratford produced all parts and all packaging of the sets happened in Detroit, hence why all 1961-64 LEGO Samsonite boxes for the US market have "Printed in the USA" on them. That would leave Loveland only responsible for packaging sets, giving more time to set up shop, but of course that's just an idea. Loveland on its own provides a nice explanation (and timeline given the work we did above) as to how these sets could've been ready for Christmas of 1965.
I know what you're thinking. Can we prove these were available for purchase Christmas 1965? Yes.
Remember those newspapers from earlier? Showing them all on the page would be very disorienting for you as a reader, but I'd still like to show them, so instead I'm linking the images below.
I will list the sets displayed in the newspapers from the clippings I picked out(keep in mind this is nonexhaustive), just know that some sets are not explicitly listed but instead are identified via their prices.
After that, we'll go into some examples that need to be addressed specifically. You're welcome to explore them as you'd like, they're featured in no particular order:
Listed: 205, 041, 610, 450, 002 | Pictured: 021, 205, 041
Listed: 205, 042 | Pictured: 205, 042
Listed: 1961-1965 sets | Pictured: likely 004 and not 704
Listed: 001, 002, 610 | Pictured: 001, 002, 610, 021
Listed: 021, 610 | Pictured: 021, 610
Listed: 120, 004 | Pictured: 120
Listed: 001, 002, and either the 246 or 799
Listed: 042, likely 041, 001, 002, 120, 004 | Pictured: 042, likely 041, 001, 002
Listed: 042, 120, 004, 285 | Pictured: 205, 042
As with the last example, some 1961-65 sets were being advertised alongside 1965+ sets. The image below, however, demonstrates how newspapers make mistakes, and I'm not sure which part to trust of this one:

And of course, as you can find plenty of examples of in the Advertising section of the site, this does not mean all newspapers showed 1965+ sets. Some stores, like below, did not advertise having the new assortment:

Still, some may rightly question everything thus far. If we found a newspaper in error, are we just cherry picking anything that confirms our new release date? How can we be absolutely certain that these sets reached shelves in 1965?
Remember the prototype boxes? Remember how the 042 Jumbo Brick Pull-Toy had the most unfinished prototype?
It seems even the roughest prototype set reached store shelves in 1965, as Burdine's was able to take a custom image of the 042 alongside unrelated products including Dijon mustard:

That is absolutely, definitively not a prepared image from Samsonite, meaning that store had it in hand and could take pictures of it before the publication date, December 5th, 1965.
But wait! There's more evidence! A late 1965 edition of Playthings shows some of the finalized boxes in the 1965 line in association with the Loveland plant:

And this next magazine scan, from October of 1966, cites the new assortment as having won "the Gold Award" from a competition of packages:

I was able to track down this competition, but not any clippings or documents that specifically declared Samsonite's award. A newspaper from February 1966 cited there were over 7,000 entries and had already been evaluated by February. That further confirms these boxes were ready in 1965, as evaluating 7,000 entries would take judges quite a while.
Conclusion
And so, I think we've reached a very sound and well-rounded conclusion. I've poured through everything I could think of, thinking through any way this could be evaluated—we've demonstrated all that could be problematic and shown more than enough examples to demonstrate this is not an anomalous mistake, this is actually what happened.
That's largely why this article is as exhaustive as it is. While I do not trust aggregate catalogs like Brickset or BrickLink, when they all agree on 1966 and all other sources have said 1966 and have done so for decades... I want to check my work.
It's interesting to note that I completely missed these clippings before, as the word "Samsonite" is missing from a lot of them. This is likely because Samsonite's name was significantly reduced on 1965 packaging, as well as Samsonite's own marketing(as toy stores were not writing all these up themselves) shifting away from association with themselves.
Out of all the investigations we've done thus far, this one feels by far the most important. It informs the larger Samsonite narrative, as dates are immensely important to figuring out exactly where and why things happen the way they did.
So now we know, and can show, that all those sets(041, 042, 205, 285, 005, 003, 004, 120, 021, 450, 375, 615) released in 1965. But there's still another question, as there are two sets still unaccounted for. Did the 022 Doll Furniture and the 005 Discovery Set still release in 1966 (as I previously thought), or can they date to even earlier?
Both of which are explored in-depth in their own dedicated articles.