the bases are very different in size. if it looks like a foot long then thats the bigger base. i want to say that if the base is taped inside the box then thats the bigger base since that was my experience. maybe thats a quick way to tell if the monitor is one that will work or not?
i dont think the bases make a difference. i have two of them with different bases, and they both work fine. i had one with the bigger base that had problems, but then exchanged it for another one that ended up having the same bigger base and it works great.