THere is a program that occasionally appears on History Channel about how the Russians copied the B-29 after WWII, from four B-29s that were landed in or near Vladivostok, after having made "deliveries" over Japan.
Stalin ruled that these B-29s must be duplicated "exactly" in every minor detail - including the radio and electronics, and this involved copying US made and designed tubes. The Russians even had a couple of nicknames for the B-29s, "Dar Bozhie" which meant "gift from God" and "the brick bomber" because it was copied "brick by brick" in their terminology.
So, here we are 60 years later, enjoying the unintended audio benefits of this "reverse engineering" project in Russia.
/ed B in NH