Dating mullard valves
If you find the tube in North America, assume the European code is correct.
If you find the tube in Europe, assume the USA code is correct.
Vacuum tubes were simply a commodity that everyone needed like batteries or light bulbs are today.
For the most part, back then no one cared when a tube was made or who made it, they just wanted a good product that would work and bring their radio, amplifier or TV back to life.
From the Panasonic codes at the bottom of the link ( onclick="window.open(this.href);return false; ) that "thousandshirts" provided the B stands for Mullard and the V stands for Bharat Electronics India So is this Sylvania actually a made in India Mullard short plate 12AX7A?
Thanks Hello Okiwaso- Yes, the first is a Blackburn made Mullard, the second is Bharat Electronic Limited (BEL) made in Bangalore, India.
When trying to identify a tube it makes the most sense to first determine where it was made. Depending on where it was made, you there are different clues to look for.
Often, the printed brand or printed country is incorrect.
Which is part of the reason it can be so hard to figure out today.