One rare, tested strong Mullard 1600 12AX7 ECC83 with long graphite WELDED plates, copper grid rods, square getter, and bullet top. One of the earliest and best-sounding ECC83 12AX7 ever made.
The printing on the tube is good, with parts are rubbed off. Etched on the tube vertically are "1600" and "D3" which mean that the tube was made in April,1953. (See photos.)
On a TV-7 D/U, where the minimum acceptable reading is 32 and new tubes usually test at 48 or higher, this tube tested strong at 47/42. The tube was briefly tested in a preamp and it was quiet and worked fine.
Worldwide shipping by SpeedPost (express) US$40. Shipping by regular airmail (takes longer) will be cheaper. Please ask.
Questions welcome.