Yes, back in the heyday of tubes manufacturers put their labels on tubes made by someone else, but it wasn't with bad intent. Tubes cost a couple of bucks back then and most people didn't care if they had an RCA or a Mullard in their tv or radio.
It's not too hard to determine what tube you actually have these days.
Phillips tubes (Amperex, Mullard, Siemens, Valvo and many more) have codes etched into the glass. A list of the codes and how to read them can be found here:
http://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf
Telefunkens have a diamond molded into the glass at the bottom between the pins and RCA etched an octagon around the tube variety (e.g. 12AX7) into the glass near the top of the tube for a couple of examples of identifying characteristics.
The Tubemonger has a huge library of photographs of vintage tubes that is very helpful in identifying tubes.
Of course, scammers have found ways to counterfeit many tubes and there can be subtle differences between a top shelf tube and its low shelf relatives, so it is best to buy from a reputable dealer rather than try your luck on ebay, probably cheaper in the long run too. A good dealer has a lot of experience that is invaluable.
I do enjoy learning about tubes and their various qualities, though.
It's not too hard to determine what tube you actually have these days.
Phillips tubes (Amperex, Mullard, Siemens, Valvo and many more) have codes etched into the glass. A list of the codes and how to read them can be found here:
http://frank.pocnet.net/other/Philips/PhilipsCodeListAB.pdf
Telefunkens have a diamond molded into the glass at the bottom between the pins and RCA etched an octagon around the tube variety (e.g. 12AX7) into the glass near the top of the tube for a couple of examples of identifying characteristics.
The Tubemonger has a huge library of photographs of vintage tubes that is very helpful in identifying tubes.
Of course, scammers have found ways to counterfeit many tubes and there can be subtle differences between a top shelf tube and its low shelf relatives, so it is best to buy from a reputable dealer rather than try your luck on ebay, probably cheaper in the long run too. A good dealer has a lot of experience that is invaluable.
I do enjoy learning about tubes and their various qualities, though.