The model identifiers are puzzling. The current 5s and 5c goes up to A1533 and A1532. It would make sense for the the device labelled ‘A1586’ to be somehow next-generation (as it is significantly beyond the 5s and 5c identifiers). The specification of the A1524 model number is much less obvious. Painting by numbers, as it were, the A1524 should closely resemble an iPhone 5c.
Gurman speculates that the model number could represent variants of the iPhone 5s and 5c, such as antenna tweaks, which probably makes the most sense.