This saddle has a 17.5" seat and a medium tree. It does not have an interchangeable gullet system.
I have used this for everything from Hunter/Jumper shows to informal Dressage shows, to trail riding and it has never failed me or given me any problems.
Although I haven't really cleaned or conditioned it all that often, it is still in VERY good shape, with minimal scuffing on the leg flaps from the stirrup leathers, and a few very minor surface scratches that you can barely see after using oil/leather conditioner. The billets where the girth attaches are actually very thick as billets typically go and are in GREAT shape. It has velcro moveable/removable knee rolls as well.
I will be selling it with a matching 48" girth, and the stirrups and leathers will also be included. All are in good working condition. There is a tiny bit of duct tape residue on one of the stirrup leathers from when the zipper on my half chaps broke before my lesson a few years back and I had to wrap them in tape but when riding, your leg covers it and it doesn't impair the function at all.
I bought it for $625 on consignment almost brand new, used only 3 times with no damage.
As a side note, it also fits just about every horse I've had to use it on. I've had the saddle longer than I've had Beau, and when I was taking multiple lessons a week on different horses, I used it every time and never had a problem with it. I haven't had to get it reflocked as Beau's muscles changed either.
After not being conditioned/oiled for several months of everyday riding: You can see the scuffing from the stirrup leathers here, however they oil down to being nigh invisible with your everyday saddle conditioner.
(Yes Beau was overweight here, he has since been moved from that barn and is in much better shape x_x)