I (Mark S) might be one of the people Kris identified... I've posted a few of mine in the past, and don't know of another Mark S around here (although I'm probably wrong about that
)
To keep it brief, I have a legit Lemon Peel that has the same exact traits. It is lighter than one would expect, and has a definite rattle when shaken. Everything about the ball is right however, and it came from a reputable source (Hunt Auctions, who has sold many different examples).
Yours looks perfect, and I see no red flags. Would be great to know what causes the "rattle", but after 150 years, I guess it could just be some interior degradation. Awesome Ball!