I have dug some of these before and you find them used with tents ,cam nets etc
yes common to find.
Sadly these pressed metal ones do not have the following that the aluminiim or bakelite ones have.
They dont even appear in equipment books but they are legitimate.
One day we may find out more about them?
" When you're chewing on life's gristle, don't grumble, give a whistle "