Interesting to know, as I have seen 3 and 5 pin versions, funny how things change, like yourself most working knifes of my youth and a fair few that I used were about 2mm thick and splitting wood you did with an axe or bill hook.Mine looked just like yours before I wrecked it with adolescent incompetent modifications. I had forgotten about the etching on the blade.
I don't understand Janne's comment about rich kids. The bushman's friend model you have filled the niche the Mora Companion does today. Cheap but effective and an ideal beginner's knife. I used it for all the normal bushcaft purposes except batonning, which I didn't know about then fortunately or the poor thing would have been ruined even earlier. The thinness of the blade never struck me as a drawback and I still prefer a small, thinnish blade with a stick tang on ground of lightness. Fortunately, the years have taught me to take better care of my knives.
I still have a William Rodgers Bushman's Friend made to a totally different specification: it is a hollow-ground hunting knife with a stage handle a is remarkable similar to a german Hitler Youth knife.