strange markings on US Tubes

Who can explain the meaning of the dots shown on some tubes made in the USA (General Electric ?)?

Many thanks in advance. 

To thank the Author because you find the post helpful or well done.

The dots are the GE date code.  This was recently cracked and the key published by Jim Cross in the December 2010 issue of the Tube Collectors Association "Tube Collector."

To thank the Author because you find the post helpful or well done.

Thank you Alan for the information so far.

So, the secret about the "dot's" is hidden behind closed doors, unless you become member of the TCA.

On the other hand, I can imagine the effort done by Jim Cross (Chairman of the TCA) to decipher the code.

We will wait and see.....

To thank the Author because you find the post helpful or well done.