JSC Svetlana is a Russian company that owns and operates the Svetlana factory in St. Petersburg, Russia, which has been making vacuum tubes for almost a century. These tubes have been known in the United States as Svetlana brand tubes and have had the "S" logo and/or the logo (a Cyrillic S) on them. Because of a change in ownership of the former American distributor, JSC Svetlana recently lost its ability to sell vacuum tubes bearing the "Svetlana" name, while maintaining the ability to sell the tubes bearing the logo in the United States and Canada.
The Xpo-pul factory (formerly part of Reflector) in Saratov, Russia is an entirely different Russian company that makes vacuum tubes for an American corporation that controls the Sovtek and Electro-Harmonix brand names. This same American corporation now also owns and controls the Svetlana brand name in the United States and Canada and recently introduced a line of Svetlana branded vacuum tubes produced in the Xpo-pul factory. The Xpo-pul factory "Svetlana" tubes are not the same Svetlana tubes that you have been accustomed to over the years!
Rest assured that the Svetlana factory in St. Petersburg, Russia is still producing vacuum tubes and has no plans to stop.
All current production St. Petersburg factory tubes -- and only those tubes -- do bear the mark, while in the past some did not. In today's world if you want the tubes that you've come to know in the past as "Svetlana", the only way to be sure you're getting that tube is to look for the mark.