To me it appears to be a straight bore whistle. It does not appear to be nickel plated. To me, it really doesn't look like metal, although it could be heavily tarnished brass.

It might not be a mass produced whistle.

He does have a great tone. One thing to note though, is whenever you hear a whistle played through a microphone, there is a possibility of tonal alteration -- not just because of the microphone, but the sound man may dial in some EQ or compression, or whatever.