300in1 diodes

I made some notes about my 300in1 diodes. I have switching diodes, rectifier diodes, zener diodes, and germanium diodes. One thing to note is that germanium diodes are supposed to have a forward voltage of 300mV. One diode I thought was a germanium diode (it was clear with two black bands but no other markings) had a forward voltage of 600mV, I’m not sure what’s up with that, so I put it in my “unknown parts” drawer.