Rubik's Politechinca 1979 square sticker German version.  In the early days the cube was called "The Magic Cube", Politechnica used completely square stickers around 1978-1979. This version is a early heavy type, this because the cubies are almost solid.

The center has no logo, the cube has square stickers

The 1979 instructions by David Sigmaster September 1979

Some Background History :

 

Prototype

The firts prototype was made in 1975, I have this picture. My last information is that this cube was stolen from Erno Rubik after one of his presentation

 

From Cubic Circular 1 1981 Published by David Sigmaster :

At the end of 1976, he approached Trial, the major toy distributor in Hungary, and they sent him to Politechnika Ipari Szövetkezet (i.e. Politechnika Co-operative), which made plastic chess sets and similar games. Gyula Nemcsók, the chairman and co-founder of Politechnika, recalls "When I took the Cube in my hand, excitement immediately seized me. I took it to our chief engineer, who likewise recognised the fantastic possibilities. We decided on the spot to obtain the necessary capital for production". (My translation from A. Havas, Der Zauberwürfel, Wochenpost 28:23 [5 Jun 81].) By late 1977, they could supply Trial. Trial made an initial order for 5,000 Magic Cubes (as they were initially named) and anticipated that advertising would be required to sell them. Instead they found that the problem was getting enough to meet demand. The Cube won a prize at the Budapest International Fair in 1978, which led to a number of foreign orders. In 1978, Hungarians were using the Cubes as hard currency which they could take or send abroad! Hungarian customs officials now ask departing people "How many Cubes have you got?" In 1979, the Cube received a prize from the Hungarian Ministry of Education and Culture. It received the Toy of the Year awards for 1980 in the UK and Germany