I think it just presses straight into the handle. According to Levine's Guide, the highest quality tool kits had detachable knives (others had a slipjoint knife permanently installed in the handle) and the same attachment mechanism as your knife.
I don't know much about the brand. IIRC, it's not listed in Levine's Guide or Goins Encyclopedia but I don't remember for sure. I've seen a 1906 patent (unrelated to this knife) so the company is quite old. I've seen 1950s ads for some of their tool kit knives. I suspect that mine is from 50s. Yours may be older.