Mentholin is another creation of Jaap Bes (De Kralingse). It is a tobacco-free snuff aka snuff powder. It contains rice flour, boric acid and milksugar. It has a mixed, coarse grain and a decent taste. As far as I can judge, the smell and taste is different to the typical snuff powder, without being able to describe it. Sorry for that vague characterisation, but I do not know how to specify the taste here.
Since preferring snuff made of tobacco during the day, I use it in the morning or before going to bed where I do not need a nicotine rush. It is also very helpful if you need to get a good breath or need to get your nostrils clean.
Mentholin is not my creation but that of the Hioolen brothers, owners of the snuff mills around 1850. Besides the ingredients you mentioned it contains coffee and orris root, which make up the scent besides the menthol.
I really like this snuff. The coffee flavor is very good, and goes very well with the menthol. There is an earthy note present as well that I cannot identify, perhaps the orris root Mr. Bes mentioned above. The flavor is unique among snuff, and I recommend it. The flavor is very comforting and familiar somehow. If you get the chance, this is definitely worth a try.