This tube I found in my collection. I had it for very long, but never did a presentation of it, because it had no etch. But today I played with my tubes, and I found this tube, and I tried to search for an etch, and I actually found one! It was so faded that I didn't see in in normal circumstances, but today I shined my phone's flash and found that here actually an etch. I tried so many different angles to take a picture of it, but I just can't, it's so faded, that it's impossible to make it look visible in a photo, but it reads this:
This particular Soviet F40T12 was more expensive than usual, because it was a special fluorescent tube, made witch modified phosphor for better light output. It was obvious with tubes were better light output, because you could find a following number after the '40' that indicated wattage. In this case it's 40-4, but I have 40-2 and 40-1. The different number means not that the tube is brighter or not, it means at what year it was experimented. Yes, these tubes were experimental, 'cause they used different compounds in the phosphor for better light output. LB was 40-2, LDC was 40-4 and LD was 40-1, so I guess LEC would be 40-3 and LTBCC would be 40-5 but I might be wrong. This tube indeed has a very good light output for a 1991 tube. It is very bright and has descent CRI at, I would say, 70. I like this tube very much. I actually have two of these, the other one has no etch remnance whatsoever.. The ink on this particular batch of tubes had defective ink, 'cause both tubes are mostly NOS, with very little use, so etches should not be so worn down.