Very nice British Grenadier Bearskin! I am no expert on these, but it's in such good condition, it looks like you went back in time and took it from 1770 whatever. However, perhaps as it could be a grenadier drummer's bearskin (appears to be a drummer or musicians) the drummer kept it and it's been stored and kept in good condition and it's been stored in perhaps a family house addict. I saw an article somewhere, a Royal Navy Lieutenant who served with Admiral Nelson in the early 1800s Napoleonic period (I think Trafalgar) kept his uniform after his service and it's been stored in the family addict for hundreds of years and was uncovered recently, in untouched condition, and it's the only known example to a RN Lieutenant of that period to exist so far. Long story short, it could be a fake, and I'm no expert, but if uniforms can survive from around the period (I've seen some really nice Napoleonic uniforms (VERY expensive, but very nice) in very good condition, from very prestigious militaria sellers... then I think it is very possible that that this could be authentic, but when dealing with rare, expensive examples like this, it is often worthwhile for forgers and fakers to fake a hat such as this one, so you must be cautious with these. Stuart Bates, a well known hat collector, who is on this forum, has (or at least had, probably still has, not speaking for him, though) a very similar example. His hat collection topic, page 1
Don't know if you've seen it or not yet, but maybe you should contact him as he may able to help you authenticate it. That's just my insight, hope it helps. Best regards,
-Jamie