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.