The RCA 6L6G tube is a low-power early version in the 6L6 tube family. We acquired a small batch in bulk originally provided by RCA to Purotron (a European brand). The tell-tale RCA octagon and part number etched on the glass however makes it clear these were produced in the US by RCA. The construction features include tall "coke-bottle" shape, grey coated glass with bottom getters. These would have been made in the 1940's to 1950's.
Important note: The early 6L6G tubes are 19W rated and have a plate voltage rating of ~360V. This means they are not viable options for many classic and current amplifiers. They will be excellent for many small/low-power amps such as Swart amps or vintage amps like the McIntosh MC30. Be sure your amp is compatible with these before you order. Let us know if you have questions.