This is an as-new Alo's Cafe slim 'Stryke' leather seat that fits liquid-cooled Bonneville T100 and T120 (and also the Street Scrambler 900, with a very minor tweak to the mount/release cable on the bike. Takes 2 minutes.)
Ended up selling the bike before I ever mounted this seat, but I have bought several from Alo's Cafe. They're handmade, the quality is superb, and it's slim and comfortable. Save yourself the (more details: https://aloscafe-usa.com/collections/triumph-liquid-cooled/products/motorcycle-seats-triumph-liquid-cooled-slim-stryke-leather)