Would all 2BU2s have X-ray filter glass?

[Robert Grant]

I have a set that uses a 2BU2 as its HV rectifier, and, unlike most tube TV sets, the tube is not in a metal cage (the bottom is in a plastic holder and the top is open).

The old tube, which likely came with the set (Zenith, 72-09 date code) has a warning that the tube has integral X-ray protection, and to replace with a tube "of the same type".

I got a new tube, which has a "2BU2" near the bottom (probably the original mark) and "2BU2/2AS2A/2AH2" in yellow ink higher up, but a different warning: "high voltage may produce harmful x-rays unless tube is shielded".

I guess, for now, that I'll stick with the original tube, but one would think that X-ray absorning glass would have been made a specification of the tube type, no?

If not, how would one ask for a 2BU2 with X-ray absorbing glass?