From what I've seen, flanged hats go back to the early 1950s (based on my limited understanding of Drumaholic's timeline work) Note that I don't look for all sales, or record them anywhere. I just notice some from time to time.
The $850 15" flanged hats may have made that price partly because they were some era (say trans stamp or block stamp) which usually fetch higher prices than the late 1950s cymbals. The high price might also have been due to a bidding war. In addition, sales on eBay tend to have a fairly large component of "what you get on the day which is unique to that particular auction" in addition to the general patterns of what sorts of cymbals get what sorts of prices. When I say "fairly large" in this case I'm thinking of plus or minus 30% on the expected price. That's based on what I've seen with my Paiste research: two cymbals which ought to get about the same price (based on having studied 2,200 sales now and knowing what factors affect selling price) but achieve 30% different prices a few days apart. In the share market they call it "volatility".
