How to Identify Tube Manufactures

[shadowlight]

How do I go about identifying which company manufactured the 12au7 tube.  I have couple of Baldwin 12au7 Black Plates with the following code p280/59-21.  The person that I purchased it from said they were Raytheon.  Is there a decoder ring that I need to obtain to identify 

TIA

[etcarroll]

If you find such a ring, let me know, I've accumulated 50 12au7s in last 2 months, not always sure what I got. as for you;

http://db.audioasylum.com/cgi/m.mpl?forum=tubes&n=149675&highlight=robber

[richidoo]

http://www.harpamps.com/micKtubes/Identify-Tube-Makers.html
http://www.audiotubes.com/mullcode.htm
http://www.ehow.com/how_6866025_do-identify-rca-12ax7_.html (12au7 should be similar)

[shadowlight]

Thanks Guys.  Will read up on the tube identification threads.

[richidoo]

Bill O'Connell (owner of Morningstar Audio Imports and AN sponsor) knows 12AU7 tubes better than anyone I know. That's one of the great advantages to buying Eastern Electric tube gear, is to gain Bill's help in finding the right tubes for your needs.

[etcarroll]

Just pulled my RCA Blackplates and put in the SIEMENS CV491-12AU7-ECC802/S-K1007 you lent me. Right off the bat struck  by an impressive open "air" at the top end. The soundstage is large even with solo piano. The midrange seems ruler flat, and the bass is tight and accurate. Of course I'm listening to Beethoven's 4th and 5th Concertos over and over, and Mussorgsky - Pictures at an Exhibition
Original Version & Orchestration by Vladimir Ashkenazy with Vladimir Ashkenazy playing solo on Piano.

Kind of seems I'm playing music the Siemens would hit out of the park. We'll see how they compare to the blackplates when I roll up to some jazz CDs, and the new Kings of Leon should be a good test as well.

How do I go about identifying which company manufactured the 12au7 tube.  I have couple of Baldwin 12au7 Black Plates with the following code p280/59-21.  The person that I purchased it from said they were Raytheon.  Is there a decoder ring that I need to obtain to identify 

TIA

[shadowlight]

Just pulled my RCA Blackplates and put in the SIEMENS CV491-12AU7-ECC802/S-K1007 you lent me. Right off the bat struck  by an impressive open "air" at the top end. The soundstage is large even with solo piano. The midrange seems ruler flat, and the bass is tight and accurate. Of course I'm listening to Beethoven's 4th and 5th Concertos over and over, and Mussorgsky - Pictures at an Exhibition
Original Version & Orchestration by Vladimir Ashkenazy with Vladimir Ashkenazy playing solo on Piano.

Kind of seems I'm playing music the Siemens would hit out of the park. We'll see how they compare to the blackplates when I roll up to some jazz CDs, and the new Kings of Leon should be a good test as well.

That was my impression also with the Siemens.  

Edit:  Forgot to mention that the Siemens were made  by Mullard according to the seller and confirmed using one of the link that Rich provided earlier (http://www.audiotubes.com/mullcode.htm).  Copied your post to Tube Rolling in Purity thread.

[etcarroll]

You're such a good boy.