I was scraping the rather thick finish off a probably Chinese made "free" bow and ended up getting a speck of the finish material in my mouth.  It tasted sweet.  That sets off a warning flag in my head that some of the finishes on the assorted inexpensive violins and bows might contain lead acetate, which is still used in many parts of the world to speed drying.

Sealed in a finish like that, I don't *think* it would be a hazard to adults, except maybe being worth a bit of extra caution and a dust mask and proper disposal if refinishing.  But I thought of the assorted "cute" vids I've seen of toddlers with those teeny 1/32 or whatever violins.  It might seem like a cool idea to parents wanting to encourage an early interest in music, but I think there might be some chance that the finish and possibly the coloring materials may not actually be safe for small children who might put the instrument or bow in their mouth.  If someone did want to give a small violin to a small child as a gift, it might be an idea to call the local board of environmental health.  Take the instrument in to their office and they have a scanner that could tell if there are heavy metals in it and if they are at a level high enough to be concerned about.  It wouldn't hurt or mar the instrument at all, and then you'd know for sure it was safe.

There have been some problems over the years with Chinese manufacturers using lead-containing pigments and finishes even on items marketed as children's toys.  I really doubt the rules about such things even address musical instruments, so it might be better to be safe than sorry.

I doubt anyone here would let a toddler chew on an antique violin or bow, but any finished wood made before recent years might have lead or other heavy metals in the pigments or finish. 

Most of the worry would be from small children chewing on the finished wood or (lower risk) repeatedly handling such an item and then putting their fingers in their mouth or etc.

I may be worrying about nothing here, but I figured I should kick the idea up in case it may be of interest to anyone.  We had lead problems with my youngest child, and had to do some lead removal of old paint on some window frames, so I tend to maybe be a bit more likely to worry about such things than average.