I have found a blister pack of 4 dark blue capsules with NO markings at all except for a LOT and EXP on the packet.

If there is no chance identifying these capsules, is there at least answers for:
Do prescription drugs ever have no imprints?
Therefore, is it black market or just definitely non-prescription?
Or are there times when a doctor will prescribe capsules with no markings/do they exist in the prescription world?

Thanks for any help