2 tubes pt55 = ts55 Philips Italy Monza plant 

selected tubes for postal service amplifier

long life tubes power pentode with markings of Air Force A.M. 

gold coated glass

wind mill mica on top,

same year 

same code #543 

tested strong at 11.5mA & 12.5mA with 200 volt on anode (reference good at 6mA) on tube tester Funke W19S 

price is for one pair of tubes = 2 tubes = two valves

TS55 = PT55

upgrade of 18013 tube

Philips made in Italy

Monza plant

year 1950's

Socket Europe side contact P8A Top contact with a cap

Telephony telecom postal tube long life

Filament Heater Vf 4 Volt / If 1.3 Ampere / Indirect

box 204

pair 3