I bought a second 26" bass drum (virgin) for my kit on January 12, 1980. It is a 6-ply shell but has a pointy B/O badge, number is 1785770. I would assume this drum was manufactured sometime in 1979. It was on the sales floor of a music store, so I'm not sure if it originated as a special order for another drummer or it was subtracted from a larger kit.
Also I order a couple of additional toms on June 6, 1981, these were 6-ply shells with rounded B/O badges (2243195/2243205). So these were definitely manufactured in the summer of '81 and thus have the rounded B/O badges.
So, Ludwig six-ply shells started to be manufactured sometime in 1976, and pointy badges got replaced by rounded ones sometime in 1979. Therefore, my toms are consistent with other drums from the 6-ply era (6-ply with rounded B/O badges).
However, my bass drum is a most likely one of those transitionally badged shells or it's slightly older than I think it is (possibly manufactured in '78 and sitting longer than I thought - though I don't recall it in the store I frequented during that time).
I would definitely pull a couple of drum heads (if you're not using clear heads) and check to see whether or not you've got 3 or 6 ply shells - it's 99.99% probable they are 6-ply, but what the heck, sometimes ya just never know with Ludwig.