After xmas,ill have to try a tung sol black plate.http://app.audiogon.com/listings/tubes-tung-sol-matched-quad-6550-black-plate-from-1960-2014-11-23-accessories-07022-fairview-nj
Looks like the seller dropped his price. Great tube. My only concern if you would be interested in these would be are they black or grey plates. The date code indicates grey plates. There are 3 versions of the black plate. The oldest had a 3 getters on the top. Most common are the ones that have a single getter on top and 2 getters on 1 side. The last had a single top getter and a single getter on each side like the ones in the picture. I had all 3 types. The picture looks like black plates but pictures can be deceiving. I found a pair on ebay the seller said were grey plates and the plates looked grey but they were the most common black plates due to the getter arrangement. The sound difference between the black and grey plate is very close with the black plate being slightly warmer sounding.