Chassis potential of an old transformerless valve / tube TV
The first valve/tube TV sets in Britain (TV started in 1936) generally followed the design philosophy of the mains valve radios of the era: a double-wound mains transformer with secondary windings for valve HT, plus heater voltage, often with a separate winding for the HT rectifier valve heater. The chassis would be at earth (ground) potential. However all was not safe because many of these got the EHT for the cathode-ray tube (CRT) from a separate (oil-filled) mains transformer, capable of supplying around 5-11 kV (depending on screen size) with a lethal current capability. The sets were heavy, expensive, and dangerous to service. They are very rare now, and if anyone obtained one, they should be very careful. if it doesn't electrocute you, it could set your house on fire.

After the war, when TV got going again, mass-production demanded simpler and cheaper designs. All the valve heaters in series and a half-wave rectifier for the DC HT, and flyback-derived EHT for the CRT. The chassis was connected to one side of the mains, and as long as that side was the neutral one, to answer your question, these chassis would have, effectively zero voltage difference from earth, but woe betide the service person or meddler if the plug was wrongly wired, or, if two-pin, reversed, or live and neutral reversed in the house wiring. 

This carried on until the 1970s or so, when some color/colour sets had power supplies using a bridge rectifier, with the chassis always at half mains voltage, whichever way around the plug was wired. 

Service people in the era, and hobbyists restoring them now, tend to use a double-wound isolation transformer between the AC supply and the set. People getting these sets generally think about replacing lots of capacitors (and they know which ones they are) before even applying power, and sometimes they use a variac between the AC and the isolation transformer primary and bring the voltage up gradually, watching for smoke or signs of life.