The two tubes at left are real RCA and Sylvania 6L6GC tubes. These are followed by National and Raytheon tubes falsely branded "made in England", and then by a tube correcctly branded "made in Russia". Note the taller bulb of the Russian tube and the fact that the black base is slightly larger than the glass. I have also seen Russian 6L6GCs branded "W. Germany". The word "England" should be a red flag to a buyer. With the exception of Brimar, most British tube manufacturers labeled their tubes "Made in Great Britain".
Compare these and the fake 7581A listed in the Hall of Shame.