I always thought it was Original Oyster Black too and I assumed it was the same set at Ray's Music Exchange which definitely does not appear to be BB finish. Hard to say with 100% certainty since they all look pretty much the same from a few feet back.
When I was in a Blues Brothers band I was always tempted to seek out a Slingerland set in Red Satin Flame like Willie Hall had in the movie but never did. Perhaps if I had stumbled onto a deal on such a set I would have snagged them. The band's leader, however, kept wanting me to have a blue set to use (he was obsessed with things being blue because it was the BLUES Brothers) and wasn't real thrilled with my orange Gretsch's...but couldn't do much about it. I doubt a red set, no matter how "authentic" would have met his criteria. I did use my larger OBP set on a couple of occasions (gigs where I thought WFL III might be in attendance, although he never showed at those gigs, only when I had the Gretsch set) but that failed to impress the band leader even when I pointed out that there were similar drums in the movie.
Since 2012 when the band broke up I've acquired a very nice Blue Sparkle Ludwig set that I thought I'd use if we ever had a reunion (just to make him happy) but that seems more and more unlikely with each passing year.
Thats a good story, KO. I bet you will end up having that reunion. The Ludwig Blue Sparkle sets look great...like Gary Lewis's set in my avatar. I always liked them. My band from 1980 planned a reunion gig this year , on the 40th anniversary of us playing Maxes Kansas City on April 15, 1980. Covid killed that plan, but we are hoping to do it in 2021. And the good thing is, I have finished restoring the same set set I used that night, so it will make a "return engagement"!