I just got this McCoy circus car. From the outside, it looks like any other Sultan the Camel car - a fairly common item. But inside, it has an electronic music box that plays circus music, as seen in the second photo. It plays clips from half a dozen typical pieces played on the calliope - Entry of the Gladiators, Man on the Flying Trapeze, Bicycle Built for Two, etc. That's a nice feature, compared to so many musical accessories that just play the same song over and over. Sound is pretty good, with a big speaker. There's also a volume control, and a big capacitor so the music is not interrupted by roller bounce or track issues. I'm not sure if the sound clips are electronic or if they are made from recordings of a real calliope, but they sound good enough that they might be real.
I've never seen a musical McCoy before; have any of you? It's not mentioned in the book The McCoy Story. The seller said he special ordered it new from McCoy. I was surprised to be the only bidder on the eBay auction, since a fair number of people collect McCoy circus cars. Anyway, it should be a fun attraction for the kids at the toy train museum.