Can a 5z4 tube be a metal bottle?

I did a thread on some tubes unfamiliar to me and recieved great info. The 5z4 rectifier seems to come in a metal and glass bottle from what I have seen thus far. I also wanted to know if the GZ30 tube would sub for the 5Z4. As always enjoy the music.
Look like my question went on deaf ears. However I did find two pics of 5Z4 tubes that are in a metal case. Quite different from the glass tubes I'm used to seeing. Now if I can find the subs to these tubes it would give me some other choices.
I tried to respond yesterday, but my post didn't make it. YES- the 5Z4/CV1864 was manufactured with a metal envelope as well as glass. The CV1863 and CV2748/CZ30 were both designed to power up to 40 watts as well, and will replace it.
Rodman9999 again you come through. I have some tubes I saw on another site that I might try. One is a GE the other a RCA. The pre should be here next week. Stay tuned.
Either of those would be good. Mullard made some nice ones too.
Ah the famous Mullard. I have a pair in my current pre (6922,6dj8). Very nice indeed. How common are the Mullard 5Z4 tubes Rodman99999?
People generally lump all the 5Z4, 5Z4G, 5Z4GT tubes together with the equivalent replacements (the CVs/GZ30). Mullard drop in equivalents are common:( ( ( (
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Guess you'll have to copy and paste that URL if you want to see Tubeworld's offerings.
Wow Rodman99999 nice links. I don't know the current brand of rectifier tube in the pre as of yet but if it's not a Mullard or GE,RCA I mentioned it's outa of there. The OD3 you advised will be ordered shortly. Thanks again : )
Enjoy your music!!