The 6-8B current stabiliser is known as a Barretter in Europe but as an Amperite in USA. Amperite is also the company name.
The figures of the Type designation describe the operating characteristics. The 6 represents the threshold stabilising current of 600 mA and the 8 is the threshold dropping voltage, in this case eight Volts.
The filament is a single wire presented as an open coil.
The lettering only became visible during photography and afterwards it was much easier to see - when you knew where to look.
The wide glass tube envelope is 28 mm in diameter and, excluding the UX4 base pins, is 79 mm tall.
