do most boxwood flutes have a finish on the boxwood, like shellac or varnish? Or is it bare boxwood. If it is bare wood, doesn’t the boxwood get dirty from contact with hands?
I have a 1820 D’Almaine boxwood flute, without a finish, and it is a nice golden color, not dirty at all… 
I’m not certain there’s any simple answer wolvy: Different makers over the years have tended to use different methods for finishing boxwood instruments.
Boxwood does tend to yellow, both with exposure to sunlight, and with oiling. Boxwood can become discolored from handling, most commonly if one tends to play with really grubby hands. 
OTH, many makers have used some sort of finishing process that repels a certain amount of dirt, grime, finger oils, and what have you, but it it really depends on the process, and how old the instrument is, since certain finishes are more durable than others.
I wish there were a simple yes or no answer to your question, but…
Loren
Some makers also apply a stain with a nitric acid solution that gives the boxwood a nice honeyed tan color; my Wilkes Bb has this treatment and I like the look more than the standard blond color of boxwood.
I have a Burns boxwood C without finish and an Olwell
boxwood D with finish. The former isn’t getting dirty.
Casey has lovely boxwood, by the way.
I took the high shine off my new boxwood flute by washing it with a hand cleaner that has some fine pumice in it. Just enough polish was left to make it pretty but not garish.
How dark can fuming with nitric acid cause boxwood to get? I have a fairly new cocus head-joint that has been fumed with nitric acid. It looks as old as the old Rudall (1835) on which it sits.
Hesperus (aka the beloved boxwood Murray) is more of a caramel or reddish gold – like our local clover honey if that’s not putting too fine a point on it. (Almost lancewood red from what I can tell … in fact, I thought Damien Stenson’s lancewood flute was a relative of mine but it was at a distance, OK?)(thanks, WD, for straightening me out!)
I assume it’s been fumed, though I was also told by someone who knew it in its earlier life that it used to be more yellow.
It doesn’t appear to have any finish or sealant on it other than a sort of hand-rubbed glow. It doesn’t seem to get “dirty” per se, though it is darker red at the grip points.
FWIW, my blackwood Murray doesn’t seem to have any other treatment, either – just steel wool and oil from the look of it, but in both cases the wood is exceptionally fine-grained (finer than anything else I’ve seen); the blackwood flute almost looks like Delrin from afar.
Some times they put a nail in the Nitric acid to give it a redish hue.
I wanted to try fuming with Nitric acid, but Homeland Security is making it hard to get! I guess some unsavory fellows can make nitro glycerine with it… ( Now I am in trouble…) 
Another reason for promoting good handwashing practices.
Also, I would think lipstick would stain it quite badly. Probably best not to wear that when you play!
…never do, myself… 
Regarding stains etc, I have read that Gustaf Stickley used ammonia to fume the white oak in his mission oak furniture. I wonder if putting a boxwood flute into an ammonia tent and fuming it would give it a nice color. It might do the same thing as nitric acid. Just a thought.
- t