This isn't vintage, but I wanted to plug these drums and especially the seller- Matt at Musicforall.biz for exceptional service and value. Check out their site if you're in the market for new music equipment.
Apparently, this kit was a leftover 2016 kit shipped from Ludwig in Monroe, NC. Fit and finish are great and I'm really digging the turquoise glitter. I ordered a matching 14" floor tom through Matt as well with delivery estimated at 3 to 12 weeks.
The Keystones sound like Ludwigs; they have the warm thump, but with more bite or attack and they're louder than Classic Maples. Their weight is similar to that of 3-ply Ludwigs- very light in my opinion.
They came with Remo Emperors, but I've changed the tom batter heads to coated Ambassadors to warm them up and still allow tone. No dampening is needed on these, but I seldom use any dampening.
Sizes: 16x24, 9x13, 16x16. Shell layup is 2 ply red oak and 3 ply hard maple. Made in USA.