This is a lightly used Humes & Berg Stonelined horn mute. It has some marks on the corks and its paint has faded a little bit from its new bright white hue, but it will do what you need it to do. Sitting here next to this red felt pen, I touched up the red trim after the photos.
This is a classic fiber straight mute for double French horn made by Humes & Berg in East Chicago, Indiana. It's light, has a stable soft sound without too much brassiness, and is fairly tough. Fits all bell styles. 4.7 oz, 132g.