Drummond voltage testers were the ONLY test lamps allowed to be used in our company during my training. They were issued to all the trainee electricians. The old Square D solenoid voltage testers were issued to all the qualified electricians.
The Drummond's were i know, the standard issue to both the old Essex and the London electricity board electricians, could still be the standard issue too. Now they are some of the most expensive voltage testers on the market, ...i just had a quick look!! lol!!!