General Overview
Thank you cheap_ass_bricks for a better image of this set!
In short — virtually nothing is conclusively known about this promotional set beyond the window it operated within. The contents are also a mystery, but there are very likely possibilities we can infer.
It most likely is from a promotion in 1966. The two currently known examples, with dates between September 1966 to April 1967, matching known distribution windows of LEGO Samsonite product based promotions. This is most commonly seen with Kraft, in that it'd begin sometime late in the year and finish mailing out by mid-way through the next.
There is a slim possibility for it to have been from the late 1966 Imaginations Inc promotion, as the two boxes we don't know of (042 Pull Toy and 695 Bulk Assortment) would be much larger than those seen above. The PO Box is also out of Denver Colorado instead of Newark, New Jersey. It could be an alternate box for the 1:87 cars and garages, but it seems unlikely as several have been found and all use the standard LEGO Denmark 1:87 box.
There is also little chance for the 1966 Oxydol promotion, as I don't think that this large of a box (or any box for that matter) would be needed for an idea book.
As it does not match anything currently available or is known to be missing, it is most likely from a late 1966 promotion that has not been properly archived. I feel a product-based promotion is more likely, similar to that of Oxydol or Kraft, given the relatively lax window. Published promotions, i.e. The 1968 Parade Magazine Promotion, typically only existed within a very narrow window.
It could have been product related like Oxydol, in fact we know of at least one 93-piece set in a similar sized box, only with a different label and fulfilled by Procter and Gamble themselves. So there's definitely a connection there, but not everything maps as cleanly as I'd like just yet:
We just don't know currently. While I suspect this is just a 093, I prefer to keep this entry separate at this time.
Contents
The question would then become: what's in the box?
There's not much to go off of, but my assumption, given the size of the box and known Samsonite assortments at the time, is that it is a 93-piece set with B-2187 inside. The 93-Piece Set evidently had been created in 1965 and was given a promotional/dealer 'B' code on the form number. The set had to be used in some capacity before the 1968 appearance, this may be one. It'd make sense, as the 702 was used as a trial/introductory set, the 93-piece set could've been used in the same way.
That's what I feel is most likely, not necessarily what is true.