Nobody here has any info on this?
Chess piece historians: What is the history of swapped finials?

The earliest set that I know of with opposite colored finials on at least one piece was the original Dubrovnik set designed specifically for the 1950 Chess Olypmpiad held in Dubrovnik, Yugoslavia.
A later "Zagreb" set had opposite colored finials on the kings, queens and bishops. House of Staunton has been offering a Zagreb set for quite a while. They claim it's a reproduction of a popular set used in tournaments in the 1970's, but I've yet to find photographic evidence to support that assertion.
There are opposite color finials on a lot of 19th century sets... glance at these for example: http://www.chessantiquesonline.com/rochford_collection/Euro_Playing_Sets.html
It's at least an 18th century thing if not earlier.
The whole opposite color Bishop and Bishop only thing seems to be a lot of Biedermeier chess sets and then later Old Vienna Coffeehouse sets seem to just about entirely have only the Bishops finials opposite colored.. .by then Staunton sets were pretty common, in these other countries the Bishop was a "runner" or some other not Bishop animal and the mitre made less sense than some kind of other mark. I read some chess tournament rules once which stated that the Bishops must be marked with a mitre or an opposite color top, making these Vienna sets as legal as Staunton sets but other styles not so legal... not sure where that is, maybe someone can find it... meanwhile in the Soviet Union it seems opposite color Kings and Queens and other pieces kept on being a thing.
Biedermeier set with "hats" also has opposite color rooks but the rooks are clearly marked in other ways. http://i.ebayimg.com/images/g/hVYAAOSwstxVKq9l/s-l400.jpg (You're not going to mistake them for pawns.)
FIDE rules, not sure when this rule was coined "2.3 Form, style of pieces Recommended for use in FIDE competitions are pieces of Staunton style. The pieces should be shaped so as to be clearly distinguishable from one another. In particular the top of the King should distinctly differ from that of the Queen. The top of the Bishop may bear a notch or be of a special colour clearly distinguishing it from that of the Pawn.", but it's still in the 2014-2015 rules here: https://www.fide.com/FIDE/handbook/Standards_of_Chess_Equipment_and_tournament_venue.pdf
OK.
I've seen old photos of "normal" Russian sets with same-colored finials. Then there seems to be a period where the King and Queen have swapped (opposite-colored) finials. Then, there seems to be Yugoslavian sets with swapped. bishop finials, and during about the same period there ALSO are photos of sets where both the King/Queen AND the bishops all have swapped finials. All of this, of course, is outside of the more modern "Zagreb" design interpretations, started I believe by Frank Camaratta.
Does anyone here know the actual progression of all these "swapped finial" designs, why it happened, what years and places saw the emergence of the different swapped finial designs, and any other info on this phenomenon?
I love swapped finials, I have chess piece sets with all of the above different styles, and I'm really curious about the history of these designs!