There are versions of this tube with extended ratings for industrial application which are designated as 6AQ5A (with controlled heater warm-up characteristic), and 6AQ5W/6005 or 6005W (shock and vibration resistant).
This passage describes variations of a tube intended for industrial applications. Some versions have extended ratings, including 6AQ5A with controlled heater warm-up characteristics, while others are designed to withstand shock and vibration, identified as 6005 or 6005W.