The old Crosby Prix de Nations were the old style FLAT close contact, no knee roll, no thigh block and what was referred to then as a "pencil roll." Most commonly seen in bridle leather. If this sounds like what you have, check out the prices on eBay
and see what they're going for - they've held their value pretty well.
Photos would be a big help, as would a serial number (Crosbys have then stamped into the leather on the underskirt, a description or photo of the saddle plate or the the nail head.
If it's a 17.5" with a wide tree, I might buy it from you.