The Museum has several thylacine specimens. This is a skin - it has been preserved so it doesn't decay, but has not been stuffed like the mounted skin has.
Most animal skins in the Museum are kept in this way - the skins do not get damaged and they are kept away from the light so they do not fade. It also saves space - the Museum has limited space, and storage is very important. Skins are only mounted when they are to go on display.