I can't add much to this particular discussion, but would like to add this picture from a 1937 F Herder catalouge, it shows that there were other knives specifically aimed at the market for a knife for young boys,( I presume these are DJ) it might go some way to understanding why not all DJ boys were wearing a HJ knife and chose another type.
A translation from the top of the page
"Every boy's desire and pride is a fine sheath knife. So it goes through thick and thin, through rain and sunshine. Everything is cut with a knife, bread, sausage, cheese, twigs and even roots have to be used to dig them up. What does the fine, bright blade look like after a short time! Rust will set in when rubbed, losing polish or leaving black spots. To remedy this evil, we have produced the stainless Constant sheath knife, which is thoroughly stainless and very sharp. Adults also appreciate this sharp knife for boat trips, camps, picnics, hunting and fishing."
Gary
