Tube says RCA and EJ in orange and silver writing says 4BL8/XCF8 also GT Britain

Can't tell you anymore. Got left these by my father when he died and I am liquidating his tubes. He was a ham enthusiast and fixer upper buyer/seller. Just going by pricing I see online, make me an offer. Anything I can do to check them out let me know.  I have limited tools: a multimeter if that helps. All items "as is".