OTK is the QC check and #59 is the technician number who tested this valve, if the failure of this tube causes a military loss they will go to the factory registry to see who was technician 59 who approved the defective valve and his career over and possibly a vacation in Siberia for 10 years, this was the good news.
The bad news was that this tube was rebranded by New Sensor and the year was removed, for what I know Russian tubes always used direct year/month info, they dont used year code as US tubes.
