It's a cool set. That's for sure!
I have a "70's" Ludwig Deluxe Classic kit -blue sparkle. None of the shells have date stamps and two of the drums have B/O badges with no numbers. The un-numbered badges indicate 1970-71. The floor tom has a B/O badge that indicates the year of 1976. After that, I found a near-mint B/O Supra that had a badge number indicating it was made in 1979.
My point is that ALL the drums are clean and look as if they could have been made on the same day. Blue sparkle is a common sparkle finish and it hasn't changed in all those years (as far as I know). The wooden shells are all 3-ply with maple interiors and look exactly alike. Visually, the drums match. But, serial number-wise, they are not a truly matched kit (by the standards I go by). Ironically, I have seen "matched" kits with different shell layups -similar to what the citation by Mr. Ludwig suggests happened. The bass drum and mounted tom might have painted interiors, but the floor tom might have an unpainted mahogany inner ply. And that would be considered a matched kit, whereas my blue sparkle kit would not. Weird, huh?Mind Blowi
So, it IS a strange and inconsistent system for determining what a matched kit is in the collecting world.