Starting in the 1950s the folks at TLG gave out small souvenir sets for visitors to Billund. Of course they are not as nice and expensively exclusive as the Inside Tour sets available to visitors today.
Possibly the earliest souvenir set from TLG was a 1958-63 era tiny set that fit nicely into one of the LEGO spare parts packs of that era. Whether you just drove up and knocked on the factory office door is debatable, but TLG did offer their early visitors a nice little sampler of LEGO parts.
Here is a 1958-60 box with parts and brochure in Danish...

And here is a 1960-63 version of this same set, but with a universal "LEGO System" outer sleeve, and an updated brochure. This shows what you can build with this tiny set. Also of interest is the inner sliding drawer to the box. This shows the bottom. Apparently TLG must have produced a lot of these, since this is still a 1958 inner drawer with a 1960-63 outer sleeve. The back of the inner drawer shows all the LEGO countries of Europe as of 1958. These countries included Denmark, Sweden, Norway, Iceland, Netherlands, Belgium, Luxemburg, West Germany, Austria Switzerland, Italy and off to the side, Portugal.

The inside of the inner drawer contained all the languages of countries selling LEGO at the time.... written in the local language is "LEGO System of Play"....

In 1964, the Souvenir box was redesigned as just LEGO bricks, which were available in colorful little boxes inside this large flat box. This same box type was used in 1964 as a special Christmas issue with a sled and other holiday motives on the inner boxes.

By 1970 a new box design was introduced once again, a bit larger, and with loose bricks inside. This box had "souvenir" lettering all over the box....

This box came with loose bricks inside. It was redesigned with a new updated LEGO logo in 1974, but looked basically the same, again with similar contents.
Then in the 1980s TLG stared using boxes that appeared like regular small LEGO sets for their souvenir sets.
My Unofficial LEGO Sets/Parts Collectors Guide desktop download has a new chapter in just these unique and special sets. I separated these from the chapter on Promotional LEGO sets, and have since added more sets to the ever expanding universe of LEGO.
Comments
Between 1985 and the present several other souvenir sets were introduced, and in recent years with the "Inside Tour" some very limited edition and valuable sets were introduced, such as the Villy Thomsen LEGO Truck 4000008, and the Ole Kirk House LIT2009.
Also there are an endless supply of other promotional type souvenirs that were introduced by TLG in recent years, both at LEGO Fan sites, and also exclusives only sold in Billund.
(Note: the little guy made of LEGO bricks)
And here is the back of that box....
That little fellow is known as the "LEGO Gnome" or "Mr. LEGO". It appears that he was also a souvenir item....
This "Mr. LEGO" was also sold as a glued model to LEGO retailers in a larger size... and when you see this Billund factory image (1960)... it seems surprising that few have survived... ( I know a lot of old time collectors that would pay big money for just the "dogbone font" LEGO oval on the chest of these figures)...
And here's an American item from the early 1960s... a "Scottie the Dog" mini model. The original purpose of this simple design is unknown. Was it a souvenir for people who visited the Samsonite LEGO factory? Based on the writing, it may have been for a Toy Fair. Judging by the Cellulose Acetate red color, it dates to the earlier 1960s...
TLG made this as a complimentary LEGO set for the Volkswagen Corporation in 1963. This set was a giveaway set, but it has not yet been determined if it was for VW Showrooms, or VW corporate customers. The box contained the new (1962) red LEGO wheels with gray tires and white 2x4 axle bricks. The set also contained 2x4 bricks in yellow, blue and clear. This set was to build a LEGO balance scale.
On 2 of the 4 sides of the box it shows 4 VW Buses and Vans. Ironcally TLG made 3 of these 4 models into 1:87 scale cars with metal wheels, the pickup, the van, and the Samba bus. Only the extended pickup was never turned into a LEGO model. But these images actually are unrelated to the LEGO 1:87 vehicles.
On one side it says in German "Not for sale LEGO sample"....
A very odd giveaway...
Most of you may have forgotten about this... well at least I did... this was a 75th Anniversary of TLG in 2007 promotional giveaway.
Anyway.... here's the scoop about this set (thanks to my German friend Jan)...
This set gets much less attention than it actually deserves, since it's a strictly limited item related to the 2007 anniversary (75 years of the company). Almost every LEGO store got 50 of them, a few larger stores got 100. They were not given away for free but there was a daily competition/lottery to win one (5 were won per day), and you had to get back to the store later to pick it up or call by phone and leave your address to get this item.
But since it didn't get an item number, it seems to be much less attractive to set collectors...
(Images from my German friend Sven)
Wow... this Duck Set (and its' minimal packaging) is almost forgetful.... no wonder I forgot about it!