[1BionicEar]

The 5963 is a premium version of the 12AU7 that was made in the late 1950s and early 1960s for computer use by industry and the military.

I have a group of 5 identical late 1950s Sylvania 5963 tubes with long gray plates, square D getters, and soft gold logos.
Four of them have 5963, Made in USA, and Sylvania logos  Three come in original white boxes with 5963 stamp. One comes in generic white box.

The fifth tube has identical construction with US Army, 5963, Sylvania, Made in USA logo and comes in a generic white box.
All tubes test as-new on my Sencore tester.

I am asking $75 plus $5 for USPS 1st Class or $10 for USPS Priority Mail shipping.
Payment by PayPal.  I will absorb the fees.

Let me know if you have any questions.

Thanks for your interest.