Villeroy & Boch WC Slim seat with quick release and softclose. Have qty 2, bought €150 each but will sell at €95 each.
These are still in manufacturer original packaging and the seat is still sealed in the original plastic.

Item number: 9M65S101
White
Hinge Stainless Steel
with quick release
with softclose

Width 374mm
length 439mm
Height 48mm

further details can be found here -
https://pro.villeroy-boch.com/en/jp/bad-und-wellness-detailseite/p/Subway-Toilet-seat-and-cover-SlimSeat-Oval-9M65S101.html