I'm trying to find the notes of C&TS 489's ATSF 6 Chime as heard in THIS video. I think it's: D F G A C D, but I could be wrong. I'm planning to make a PVC replica of this whistle.
The fifth tone wavers back and forth between a slightly sharp B4 and a slightly flat C5, as shown in the spectrogram below.
Overall, since all of the notes are slightly flat, if you adjust the overall pitch upwards (to bring them closer to A=440 Hz), then that fifth note would be (mostly) a "C5".
That spectrogram plot is from Sonic Visualizer, which can be an extremely useful tool for analyzing audio files. It's freeware (GNU General Public License) and is available for Linux, OS/X, and Windows.