Do you mean 'round plate'?
V
(Yes, it's a Tung-Sol.)
FYI, these are somewhat rare and quite expensive. I have a bunch I gathered while I used 6 'N7s in 2 poweramps. While I was accumulating, I was sorting and culling them by degree of microfonics, and some were so microfonic I TOSSED them. If you're serious about acquiring some of these, e-mail me at jeffreybehr(at)cox(dot)net.
BTW I suggest you determine what functions the 6 in your preamp serve and then buy less-expensive tubes for, say, cathode-follower functions.
