Arfa Daily wrote:

I would suspect that breakdown voltage is a 'designed in' characteristic,
and will depend on physical dimensions of the transistor structure. The
"cherry picking" that the manufacturers do is usually related to gain and
gives something like an A, B or C suffix like BC108A or BC109B. How would
the manufacturer actually test a batch for breakdown voltage, as if you take
the device to breakdown, then it is destroyed. Would the manufacturer be
prepared to stake the breakdown voltage of a production batch, on the basis
of a few tested examples ? I'm not sure that he would. It's a bit like
having tested fuses really, isn't it ?

You're very mistaken.

The test is done with a current limited supply and the test is for a given
leakage current.

Due to necessity (the situation was forced on me) I've had both bipolar and
mosfet devices selected very successfully for breakdown voltage.

By these guys in fact.
http://www.semelab.co.uk/

Graham