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fkw3 different styles, from what Ive seen the round design is the most common but they are all fairly scarce. Ive owned 3 over the years, but dont activly look for them.
Huggins & Scott sold 25 different at auction about 3 years ago for $6,000 ($240 ea. on average)
link to auction
http://september06.hugginsandscott.com/cgi-bin/showitem.pl?itemid=3443
edited to add... I see Red beat me to the link