How to Tell USB rating of Thumbdrives?

I have a bunch of USB 2.x and 3.x thumbdrives and would like to figure out which is which. I can't go by the color of the ends as they are different colors, like red, purple, etc. I also have put labels over them to easily see the size, like 4 or 8GB, so I can't simply read the stats on the sticks (I know, a bad move...).

I thought that Speccy would tell me but it doesn't.

So how can I easily tell if a thumbdrive is 2.x or 3.x?? I got so many I want to give a few to friends but I want to keep all the 3.x drivers.

Any ideas?
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Thanks for the tips, ThrashZone.

Lady Fitzgerald said:

I just checked the three different brands of USB sticks I have and found that, if I right clicked on one in Computer, then clicked on Properties, all of them showed the brand name, size, and if it was USN 2.0 3.0. This may not work on all brands.

No such luck here, Lady Fitzgerald. Most came up as just Flash USB drives (attachment 2), but at least one came up as a CD/DVD drive!? (attachment 1)
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The plastic inside of the plug on the flash drive will be blue if it is USB 3; it will not be blue if it is not USB 3. This same rule applies to the USB ports on your computer.