After World War II, Waffenfabrik Bern experimented with rifles largely based on the German FG-42. This example uses a short 7.5mm cartridge similar to the German 8×33 (other prototypes used a short 7.65mm or the full size 7.5x55mm round). The mechanism uses a long gas piston and hinged lock to secure the breech. It fired both semi and fully automatic, both from a closed bolt.
From what I can gather is that the black and white picture is the model known as Sturmgewehr W+F 54.
The coloured ones are the model Sturmgewehr W+F 51. But its a strange itteration. The front handguard is the same as the 1st and 2nd generation but the buttstock is clearly the 3rd generation. Of these 35 were made for the troop trials of 1953, Serial numbers range from 101-135.
Source: Bewaffnung und Ausrüstung der Schweizer Armee seit 1817: Automatwaffen II
ISBN:3 7276 7055 X