That would be a 'Wint' saddle - these were made in 1880s and 1890s as an experimental type for US cavalry. This one looks like it's been modified a bit in post-military life, but still pretty much there. Quite a rare beastie. Here's some discussion of the Wint - https://www.militaryhorse.org/forum/viewtopic.php?t=10442 Apparently made in slightly different configurations, but that was norm for experimentals. Todd H.