Winged C refers to the SED logo, and SED is the company that used to make Svetlana tubes.
Svetlana tubes are now marketed by New Sensor. SED still makes tubes, but they are just known as SED's (with the winged C logo) and not Svetlana.
SED's are made in St. Petersburg, but I don't know where the New Sensor Svet's are made...I'd assume a Russian manufacturing facility as well (if New Sensor still has their factory there).
New Sensor Svetlana EL34's are usually compared to Mullard's which have long been heralded as a nice sounding EL34. But the SED's I think are tonally superior.