As for this particular box, it comes stocked with six Horses, but remember - you'll have no way of knowing which Horse you'll receive when opening a single box up. They come with the expected Horse price tag of 24 Farm Cash per box, and for that price, you're guaranteed to receive one of the following:
Black Shire Horse
Rainbow Mini Horse
Unfortunately, another problem inherent with these Mystery Boxes is that they also don't guarantee you to not receive duplicates if you decide to open more than one. Depending on how many of these Horses you already have on your farms from previous releases, that fact alone could actually make this box too much of a risk to purchase. Either way, you'll need to make up your mind about a purchase fairly quickly, as the box (and its contents) will expire from the store in a week's time.
Will you purchase a Horse Mystery Box for your game? Which Horse are you hoping to find inside? Which one did you actually receive? Let us know in the comments!