If a diode is glass then I take it to be a small signal type.
If the volt threshold is below .6 or .7 then it might be germanium, Schottky, etc.
If volt threshold is higher than .7, then it could be for high voltage.
I figure current limit is 3 amps or more if it is larger than 1N400x type (1 amp).
As for reverse threshold, I have not tested unmarked diodes. I picture such tests having the possibility of changing a diode's operating characteristics, perhaps ruining it.
If I needed a diode with a high threshold then I used a labelled 1N400x type.