Those are Meiji/Taisho era Army officer tassels, used until 1934, when the Army kyu gunto was replaced with the shin gunto.
The tassel you are pointing to is for company grade officers, i.e. from sub-lieutenant to captain. It is in great condition but overpriced. It should go for about 120 to 150 dollars.
The one I purchased has a stem after the acorn, it is the much rarer field grade tassel, from major to colonel.
There is a third one, the general grade tassel, which has the same stem as the field grade one, but is ball-shaped instead of being acorn-shaped. On early Meiji era general grade tassels, you can even find on the stem a number of stars corresponding to the rank of the general (brigadier general, major general, etc).
See examples of these three types of tassels put on dress swords on Ohmura san's site (they were also worn on full size kyu gunto) : http://ohmura-study.net/771.html (At the bottom, you will see an example of the Navy kyu gunto officer's tassel, which was the same for all ranks)
There are also variants of the above-mentioned, with a flat black strap instead of the golden rounded one, introduced in 1912, along with a more rugged completely black and ball-shaped one for combat situations, favoured by the Cavalry.
Again from Ohmura's treasure trove: http://ohmura-study.net/771.html