I can tell mine apart by color of the material in them, at least Winchester. The small pistol are red, the small rifle look dark green/blue, I assume the color coding is to tell them apart, or that's how I do it! This is with Winchester primers, CCI small pistol primers are yellow. These are all the primers I have used, I assume not everyone codes them like this? And as far as CCI, I have only used their small pistol primers...they all be yellow for all I know. I do have a few thousand of their #41 types...havent had any out of the box yet.
If the seller doesnt know what the type of primer they are, yep you only have a potential explosion there. They are explosive. I saw the results of what IIRC, RCBS press setup that used an upright tube full of primers. I dont know what these guys did, but they blew up the whole tubefull. The metal tube was mostly unrolled and stuck in the ceiling! I can imagine what 3500 primers could do all at once, yikes!
Russellc