The wood was intended to absorb shocks from bumps and bangs, sort of like the collapsible bumper on a car.
CZ began producing full stock models when they were allowed to use their own name, with the 550 series. I do not know of any made while they were still being forced to market them under the Brno name (600 series). Between 1942 and 1954, the original Brno made full stock commercial rifles and carbines (21f, 22f, etc) using small ring 98's. These had pencil thin barrels that made them very light, but they also heated up very quickly. The Brno model B, made on a large ring 98 in the 1930's, also had a full length stock. These were marketed to compete with the Mauser M and S.
The current CZ550 has more wood than two of the original Brno models
