Yes! They are special.
I received 6 as a gift in these days and yes, they have just that particular feature (bugs)
One of them, (in the green) also contains av
Yes, it's usually crystal clear, but I have a few without that base
I think they are from the same family, only the penultimate I don't think is, but I could also be wrong about the rest, of course, it's just my opinion