My matched pair NU 2a3 is the 1st series dual black plates with the coil springs on top. I believe this version is the oldest version of the dual black plate that came into production right after the single mono plate. One base has perfect lettering, the other base has some slight smudges, but is still very much intact. The tubes are perfectly identical in construction, however one tube is a couple of millimeters taller than the other tube. These were bought from Andy at Vintage Tube Services as a matched pair NOS about 2 months ago, and have been used at most 5 hours due to my affinity for the 45 tube in my amp.
Serious buyers can email me at recstar24@yahoo.com if they need pics.
