[35Z5]

The current rating would no doubt be dependant on condition of current limiting resistor inside base, I doubt a in spec NE-31 exists. Of course it's all about firing point, I doubt that's in spec either.  

I have a 910 plus a couple of 912 & 920, I wouldn't trust short test in any of them. Likely if short is indicated that's believable, but a small amount of leakage will never be indicated.