To be honest I couldn't test this on the CT-160 Its not in the manual and I downloaded the spec sheets for it but couldn't work out the switches for the socket. It will be NOS as I bought it at Auction in the 70's with a cubic metre of other valves that were all good.
The 6B5 is a Direct coupled output tube comprising two
triode units mounted in an ST-14 bulb. The input triode being a kathode
follower is driving the output triode by direct coupling. The input cathode and
output grid are connected internally. The cathode resistor of the driver is
part of the tube. The power section works without (negative) bias so there is
no need for a cathode resistor/ capacitor combination.
Since the output section operates with a positive bias, it requires a high-µ
characteristic to keep the plate current low. This is achieved by using two
separate control grids connected in parallel inside the bulb.
It has no box