Apparently from 1917 to 1930 Xacto was focused on Hypodermic devices.
The company did not produce interchangeable blade hobby knives until 1930.
Hopefully some pre-war literature will turn up.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !