Maybe I'm missing something here, but i don't see anything all that odd about this set.
The OP stated it had him puzzled and requested thoughts on the subject. That's what was laid out.
This is an odd bird. There are not that many Ludwig bass drums from this era with twin spurs. Fact is, there aren't that many Slingerland or Rogers from that era wearing twins either. It was very uncommon. Slingerland added twin spurs on the Buddy Rich kit in the very late 60s and followed up in the mid to late 70s with twin spur bass drums. Ludwig didn't offer twins until the mid to late 70s. The fact that this bass carries them extremely uneven points to a non-factory mod. That's relevant as it clarifies the OPs request.
Add to that the presence of a 13 inch Tom and a 14 inch floor and you add another wrinkle.
The presence and location of that model cymbal mount and no Tom mount adds yet another wrinkle.
The juxtaposition of the badge and the cymbal mount ... Yup, another wrinkle.
The bottom line - this is a very odd kit. It quickly becomes apparent that it is not a factory kit at all. That's where the members here had some fun ... How did these drums find themselves?
The OP was attempting to nail down the cat kit this might have grown from. That's what this thread has spoken to.