Whoa! This is a new one on me! A prototype? The hands are unusual, as is the case. Love the bezel, though.
This is one of the later models, issued shortly before Zenith stopped producing mechanical movements altogether, and for which next to no documentation exists. Adding to the conundrum, only a few months ago, empty NOS cases like this one were available on the 'bay. All of that said, this is pretty attractive and seems to "hang together" as a coherent piece. Might be legit. Might not. But it is "real purty."
Lou, that is exactly what I thought when I first saw it! Then again, I lived down South, so using "purty" is natcherul.
I'm saying it's a franken. Here's the case from a 70s catalog. Setting aside the possibility that the dial came in different colors, all three hands are different and it doesn't have 28800 on the dial. Also, I thought Zenith went away from adding the 28800 on Defy models once they moved from the 2562 to the 2572 (I recognize that they used it on other 2572 models).