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Is there a 12CM7?

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I have a pair of noval double triodes without any markings.
At the moment i dont have a means to post pictures but will try to do so later, so I'll do my best at describing it.

Here is what I know:
Dual triode in a 65mm tall noval base envelope.
Same pinout as 6FQ7/12FQ7 and 6CM7/8CM7.
Electrode structure looks 99% identical to 6CM7, similar to 12FQ7/6FQ7 in height (approx 20mm) but different in cross-section.
Heater glows with appropriate color at 12V and draws 300mA.

Heater is spot on for a 12FQ7 but electrode cross section is different (I have a 12FQ7 for comparison), while it is almost exactly the same as a 6CM7 and 8CM7 I have save for a slightly different stamped pattern on the plates. I am not aware of a 12CM7, but something like it would best fit the available data.

Any ideas?
Argh, just noticed I've made a major blunder. In my post I mentioned 6CM7 and 8CM7 and asked about a 12CM7, this is WRONG.

The correct types are 6CG7 and 8CG7, and I should have asked about a 12CG7!!!

6CM7/8CM7 have a different pinout and are dissimilar triodes, the one I have definitely has two completely identical ones inside.

I know 12AT/AX/AU7 all too well, and have lots of them from at least 5 different manufacturers. They use a shorter (<2") envelope, the 6CG7 has a taller envelope (2 3/8"), and the electrode structure of the triodes is also about twice as tall as for instance 12AU7. It looks 99% the same as the 6CG7 I have here for comparison, and that in turn looks very much like the insides of a 6SN7GTB, which is no wonder considering the 6CG7 is the Noval socket equivalent of the well regarded 6SN7GTB octal socket tube.
The pinout is also exactly the same as 6CG7, but I can practically vouch that the filament voltage is 12V. Therefore, apparently it would be something like a 12CG7, if such a tube existed. I cannot find any reference to it, but considering there is a 12SN7GT, with near exactly the same filament characteristics that I measure on my mystery tubes, I would not be surprised.
I have a RCA data sheet for a 12FQ7, it is actually one single page that says:

The 12FQ7 is the same as the 6FQ7 ecxept:
Heater Characteristics and Ratings:
Heater current: 300 +-20 mA
Heater voltage at 300mA: 12.6V

I have actually searched this forum and found one oblique reference to a 12CG7 in a context that suggests 6CG7 and 6FQ7 are equivalents - they are very similar but not the same. I have a Ei 6FQ7 and a Hitachi 8FQ7 (450mA filament equivalent to the 6.3V 600mA 6FQ7), and they have almost identical electrode structures, but as I said different than the 6CG7 I have, which in turn is practically the same as the '12CG7' Mystery tubes I have.

I have also just found a reference to a 12CG7 in a german tube vendor catalog. Damn expensive too, at 14 Euro...
Sch3mat1c, you are exactly right in your description of the 6CG7 I have and the two mystery tubes - the plates look like the ones of the 12AU7 but are about twice as tall.
The 6FQ7 and the 8FQ7 I have looks different, narrower plates and more 'boxy' - the 6CG7 has a rectangle cross-section, the 6FQ7 is more square.
And now for more mystery: neither the 6FQ7, the 8FQ7, the 6CG7 or the two mystery tubes have a shield. In fact, my data for 6CG7 shows pin 9 as not connected, and that's ecactly wha it is in all of these tubes.
The curves for 6FQ7 and 6CG7 I have are also diferent - not much, suggesting that the tubes could be interchangeable, but they are different.
I have also found a Google reference to double marked tubes, 12CG7/12FQ7, as well as te aforementioned seller that stocks a 12CG7 in Germany.
I guess I'll just call label them 12FQ7/12CG7 and be done with it... I don't think it will be much of an error either way ;)
There is another small mystery about these, US marked tubes (number - letter/letter - number) are very rare here, but there is an abundance of european marked tubes (ECC / PCC/ UCC etc). For example, 6SN7GT could be found as ECC32. Is anyone aware of an euro marking system equivalent of the 6FQ7/12FQ7/6CG7/12CG7?
I guess the first 6xxx would be ECC something, the 12xxx would be PCC something, but I have not been able to dig out any data indicating there ever were such tubes...
I know what you are trying to say, but there are tubes that support multiple types of heater supply.
12AX/AT/AU7 are a great example - they have a 12.6V 150mA center tapped heater, which you can also use as a 6.3V 300mA if you connect the ends together and use it between the connected ends and the center tap. The heater can be used either in parallel or series connection.
The european name for these is ECC81/82/83, but not a FCC (12.6V), HCC (150mA) or PCC (300mA) simply because it's all the same tube - the ECC variant actually serves as all of these depending how you connect it.
In the same manner, a 12FQ7 or 12CG7 has a 12.6V 300mA heater again for either parallel or serial heating supply, so it would be logical to look for the european named version as either FCC or PCC something, and I have not found either.
Similairly, 6FQ7 and 6CG7 have a 6.3V 600mA heater, and again an european marked version cannot be found either as ECC or XCC.
The odd 8FQ7 and 8CG7 would be marked as YCC for their 450mA heater current since there is no first letter for an 8V winding.
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