Pressed wood grips with the FB/VIS logos are usually encountered on earlier pistols produced in the first series. I have seen examples where only one grip was of this pattern & the other plastic. I suspect the pressed wood grips were made to either supplement or replace the plastic ones. For whatever reason, they were rejected & the limited number produced were relegated to armorer replacement part status. I believe these were only for use with the small grip screws.
As for the late Steyr grooved wooden grips, these begin to appear in the mid second series "h"-block. The "i"-block was skipped. The "j"-block pistols are all but non-existent, and they are most commonly encountered on the final run in "k"-block. An interesting sidebar: About 30 years ago, a friend of mine had a Steyr "k"-range P35(p). He took off the right grip and attached to the backside was most of a label. It was triangular in shape and depicted a maiden with German writing describing the contents as "Velveta" cheese. By that time in Germany, nothing went to waste, so it seems at least some of these grips were constructed from wooden cheese-crates!