Rare Philips 12ax7 Code Need Help

[vmazzone45]

First ID like to say thank you for having this forum here. I appreciate these forums greatly for the wealth of cumulative knowledge and valued opinions here.
I am seeking info on a 12ax7 tube labeled RCA but im fairly certain it was made in Heerlen Factory in the early 50s. I will try to post a pic. ANyone with knowledge about these early Philips Tubes. Any insight is greatly appreciated.
I am selling it on eBay and want to give any potential buyers as much info as possible. It is certainly a rare tube from what Iv learned so far.

 

[barretter]

If you Google "Philips factory valve codes" you will find a list of the codes used on valves produced by the branches of the Philips conglomerate ; and yes, indeed, the first row indicates the Heerlen factory and the second an ECC83, but I don't see why you think it is rare.

 

[JonSnell Electronic]

ECC83/12AX7 is just another valve widely used in most valve and 'valvestate' amplifiers. Not quite 10 a penny but they vary in grades. Mullard were in my opinion the best, Mazda (in the UK) the worst for microphony. I have some Russian built Svetlana 12AX7 that are really nice, large anode and very quiet. They only cost me $14 US and I have some 12AX7WGA that are also nice for phase splitters. They were cheap!
People will pay what they think they are worth.

 

[vmazzone45]

Thanks for your input. Yes barretter I have the list and there is a compilation of codes someone put together in 2005 that is helping me decipher it.
I guess the thing that makes it rare is that the stamp is on the bottom and it has the old code system. Factory Month Tube Type Change Code? and it is labeled RCA which from what I have gathered makes it August 1953 from Heerlen. Now how rare Im not sure. But other sights state that tubes like it are rare or even "ultra rare", whatever that means.
Just looking for confirmation or any additional information on it.
Thanks Cheers!
link to some info here:
Tube Classics - Philips Audio Tubes

 

[vmazzone45]

Thanks for the input. Barretter I have that list and it along with another compiled code chart has helped me decipher the code.
I guess what makes it rare is the fact the stamp is on the bottom and its labeled for RCA. Making it likely made August 1953 in Heerlen. It has welded plates and slanted D getter. Now how rare and what that means I'm not sure.
Here is a sight that describes tubes just after this made in Heerlen as "rare".

Tube Classics - Philips Audio Tubes

Just looking for any additional information or just confirmation my deciphering is right.
Thanks Cheers!