Kraft Promotion Dates (1968-1972)
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This article has been a long anticipated for myself, as I've been itching to comprehensively cover the Kraft sets in particular. Despite being basic assortments, they're very muddled in my mind and other sources are very confusing and even contradictory.
My goal here is to straighten all that out. That all starts with confirming the timeline. How do we do that? Well, form numbers will be a big help, but our main anchor will be...
Velveeta Boxes!
The source for the Kraft promotion was via boxes of Velveeta.
As this promotion ran for several seasons, we will largely compartmentalize coverage based on seasons rather than individual sets. And dating each will be rather trivial, as we have the form numbers of Samsonite Kraft-LEGO materials, newspaper reports by customers, and the Velveeta boxes themselves, which are stamped with exact dates of production.
Generally, given all the newspapers I've looked at and examples shown below, the promotion began or was consistently updated around September (as all reported orders seen below were in or around October), even though the boxes weren't updated in the marketing until ~February of the following year. All these sources have been tagged with 'Kraft' and are available for reference onsite.
The end of each promotion is a little hard to track. Unfortunately, newspaper ads are limited in this regard due to reuse of images. So a later appearance of a Velveeta box with a LEGO promotion in a newspaper isn't necessarily evidence of continual production, as retailers often reused materials from previous seasons. However, the dates found on Velveeta boxes help immensely in this regard. Typically, they are either found late in the year or early into the next. I'm not aware of any Velveeta boxes with dates in the middle of the year.
And so I think that's where we start:
How do I date a Velveeta box?
It's very simple to do for yourself. For your reference, I'm using a 1970 Congressional document quoting a Kraft representative:
"There is a number code on the front of the package. For example 105A0. The 105 is the day of the year on which the cheese was packaged, the A is a code letter for where the cheese was packaged and the 0 means that it was packaged in 1970. (For last year, 1969, the end number would have been 9.) Kraft cheeses have a shelf life of 150 days from the date of packaging. "
So somewhere on the box should be a stamp like the one seen below:

It has '230C2'. Based on the above report: '230' means it was packaged on the 230th day of the year out of 365, 'C' is irrelevant for us, and '2' means the year was 1972.
In 1973, Velveeta boxes switched to an unambiguous MM-DD-YY format, so no worries there.
So without further ado...
1968
These first two years are almost the same, with some minor box differences.
The first Kraft promotion has an earliest confirmed date of October 1968 (known via this January 1969 newspaper). The LEGO Velveeta box itself first appears in an ad in early 1969. The below Velveeta box is stamped with '042N9', meaning it was packaged in February of 1969, consistent with our late-1968 start date.
The 1968 promotion had its own brochure with a form number that corroborates a 1968 preperation:

Read more about the 1968 promotion here: Kraft Sets (Late 1968)
1969
By February 1970, the box shown in marketing was updated with the new tear tabs and the image on the back was slightly altered. Even though it makes its earliest known appearance in 1970, we can reasonably assume via the established pattern that the change happened as early as late 1969.
The boxes of Velveeta support this, as again we have a '289N9' code. Meaning a late-1969 date.
To go along with this, the Kraft brochure H-2466's form number replaced the original one. The primary difference between the two is the address for mailing:

Read more about the 1969 promotion here: Kraft Sets (Late 1969)
1970
In late 1970, the promotion was completely overhauled. Now the Velveeta box featured several model sets instead of the 74-piece basic assortment. The box first appears in marketing in early February of 1971. The offer was evidently available as early as September, as this January 1971 newspaper reports they ordered one on October 3rd of 1970.
My box gives a January of 1972 date, but that makes sense as this offer was continued into late 1971.
The Kraft brochure that came with the mailed set had a small change to the assortment (removal of the carrying case), but otherwise was the same. Its H-5105 form number implies an early to mid-1970 compilation, as it is the number before the 1970 roadplate as well as other 1970 sets, which matches our late 1970 release.

To read more about the 1970 promotion, check here: Kraft Sets (Late 1970)
1971
The "Mini Vehicle Sets" Velveeta box reappears in late 1971. This September 1971 newspaper is an excellent example, as it features the box in a unique grocery assortment image taken by the store and not by Kraft's marketing. It solidifies what I've seen across newspapers, that the promotion appeared late in the year. It'd make sense with the Christmas season in mind, as that's the best time to market a toy.
While the Velveeta box did not change, the promotion's brochure and offered sets were completely overhauled. The form number 8006 follows the established pattern, as it appears just after the 1971 contest blank for the 1972 Make a Model Contest and before the 248 Conveyor's instructions:

Another thing of note is that 1971 marks the earliest season Ad Service Co. of Denver was used for premium fulfillments. More on that in the dedicated article for the 1971 promotion: Kraft Sets (Late 1971)
1972
The new box appeared in late 1972, evidenced by this early 1973 newspaper reporting that in November, they ordered two sets at $1 each. That'd only be possible with this updated box, as before the sets were $2 each.
The date on the below box also corroborates that.


The update to the promotion evidently would've required a complete change to the sets offered. The form number 8052 coincides with a mid to late-1972 compilation, though it appears juuust late enough that a late-1973 use is possible (more on that in a second):

Though while the form number is very late in sequence, it should be noted that Samsonite had a new brochure for every season of the Kraft promotion, it'd be odd that they'd skip a year and then make one as they always had.
And because this is the most appropriate place I can think of to address this, I find it absolutely fascinating to think about the above paper in context with the ending of the LEGO license. Not only the wording "When you can't use your LEGO anymore...", but also the torn rainbow bars.
Probably reading into it a bit too much, but worth a note.
Also worthy of note, this last update in particular was an absolute mess that took several months to mop up. We discuss it further on its dedicated article.
1973
What?
Yes, 1973. I'd originally missed it, but the Kraft promotion continued for the late-1973 promotion despite the 1972 end date for LEGO production at Loveland. This can be confirmed two ways, one via surviving Velveeta boxes, which can be found with a late 1973 date, as well as via this 1973 article that reported a 1973 promotion would be taking place for Kraft. The Velveeta box did not change for this season, still offering the 125-piece set.
Other
There may exist a fifth Velveeta box, though I cannot find any surviving examples. Typically I would ere on the side of this having existed, but an example should have surfaced by now. It may be a preproduction thing (as by October 1970 they should of had already released the next wave of sets) or could just be another, rarer variant.
It only appears once in a late 1970 newspaper:

Curiously, this was the same season the Mini-Wheel Model Makers were offered for $2 each via the Velveeta box. While this box seems to lack them entirely, instead having the old assortment for the $1 price.
Just something interesting.