[Manolo]

Greetings! Today I got a stash of used tubes from a friend who inherited them. Among them, I found a Sylvania 5ar4 rectifier and various other rectifier tubes, including 2 labeled Philips 6909 274 which I presume are rectifiers, bur the designation does not have the suffix B, which is familiar to me for this rectifier. Its print says 6909 274.
I wonder if I can try these as rectifiers in my preamp. The Sy;vania is already working in my preamp.Thanks for looking!

[FullRangeMan]

Not safe try vintage tubes in your valuable hi end pré amp, you will using your equip as tube tester.

These tubes are never used ?
After 6 mounths  the getter goes tô sleep.

[Tom Bombadil]

Yes, 274B is a rectifier tube.

But a 6909 tube is definitely NOT a rectifier.  I don't know why it has both numbers on it. 

Does it look something like this?
https://vacuumtubesinc.com/index.php/vacuum-tubes/6909.html

[Manolo]

I will post a picture today. But it does not look like the one you posted. Thanks!

[Manolo]

Here's a photo

[FullRangeMan]

This is not a 6909 tube, 6909 is a decatron tube.
https://www.radiomuseum.org/tubes/tube_6909.html
Looks a antecessor of the 274A / B IMO.

[Manolo]

one can see the interior stails better...

[FullRangeMan]

There is any date code in this tube?
If no 6909 may be the date code apparently.

[Manolo]

it looks like a 274B, five pins. No date, lettering in glass is completely erased.