[Amps] Need help with switch nomenclature

[Charles Bibb - K5ZK]

Way back in my foggy memory somewhere, I remember using and amplifier 
made by B & W.   I think it was a "Model 1500", but I'm not sure.  It 
used a pair of 813's.

What I remember as unique about this amp was its "ON" or "POWER" 
switch. It used a rotary switch to turn on the various functions one at a time.

In other words:  Position 1 turned on the fan only. Position 2 kept 
the fan on, and lit the filaments. Position 3 kept the previous two 
functions on, and turned on the HV supply.

My question is, then:  What is this kind of switch called?  I used 
one of these switches (salvaged from an old tube tester) in my very 
first amplifier, and I'd like to use one again, but for the life of 
me I can't find one from my usual parts sources because I don't know 
what it's properly called.

It isn't "make before break" because it never breaks the previous 
positions.  I thought it would just be a "shorting type", but this is 
not the way any of the "shorting type" switches offered for sale operate.

I'm stumped!  Any help would be appreciated.

73,
Charles - K5ZK