This sentence uses 玉を落とす in a way that makes me think that 玉 is a noun being modified by を落とす to mean something like 'a ball intended to be dropped', in other words, a ball you'd play with in sports and the like.
Also, I'm not really sure about 何か being followed by の, is this a regular/fixed usage of 何か with any special properties?
If you need context for all this, let me explain a bit:
The person that says the sentence in question is skeptical about receiving the New Year's Gift お年玉【おとしだま】 from another person, and notices that other person is holding a ball, which turns out to contain money. Maybe it is a witty word game intended to show that the ball 玉 actually contained the New Year's Gift お年玉.