Rob Cook's book is a great resource for sure, but we generally try to answer questions here as opposed to sending someone off to the library or to the bookseller. :)
In order to determine what characteristics make one drum sound different from the next, it's easiest to cancel out the things that all (or most) vintage drums had in common with each and then see what's left over.
Ludwig's sound came from their 3-ply shells and fat rounded bearing edges.
Paint on the interiors was likely done for cosmetic purposes -to cover blemishes in the veneers...and then marketed as some kind of magical sound-enhancement after the fact.
The paint or varnish would also serve to seal the wood against moisture, too...but much ado has been made of the various coatings...none of which really have an influence on the sound...in MY opinion.
ALL the vintage "Big Four" manufacturers "experimented" with some kind of paint/varnish/sealer....Gretsch =gray, Rogers = gray speckled, Slingerland -brown AND Ludwig = clear mahogany, white, clear maple, gray speckled...etc.
Most of these finishes were likely something that came from the paint shelf at the local hardware store and not something that was invented by lab technicians wearing white coats and goggles. ;)
As far as the types of mounts...the clip mounts were older and less ideal comparatively, but, again, didn't likely "change" the overall sound of any drums.
The reason your later (Rocker) series drums from the 80's didn't sound the same is because they weren't the same shells by then. Once the vintage 3-ply shells were discontinued -somewhere around 1976- the Ludwig sound went away...but nobody noticed that it went away...because everybody was high in those days! ;)
