I don't know about Series 2, but Series 1 had a small window on the back of the bag where you could see what was inside.

 

According to the purchaser of Slug and Ironhide, the barcode letter was blocked out with a sticker.

 

My young son likes to buys a bunch of the blind bags since he loves opening them up to see what’s inside. At the stores he just randomly grabs a handful of them for checkout. I should really check but I also don’t want to ruin the surprises for him until we get home. Really it is my Transformers collection but I’m trying to get my kids to love Transformers as much as I do. We do the same with Transformers Tiny Titans. But it does suck when I’m trying to complete a series and am getting duplicates. However, we haven’t bought any of the micro changers in a long time.

 

Looks more like a Thailand store barcode sticker that just happens to be placed on top of the section where the ID letter is located.

 

So Seibertron have robot mode pictures, won't link the images but here:

Transformers Tiny Turbo Changers Series 3 Robot Mode Images

Seems only 5 new molds. Barricade, Ironhide, Slug, Ratchet, Sentinal.

Evac is blue Crosshairs, Autobot dino is a red hotrod...