percocet
 

has anyone ever received generics without ANY markings on the tablets, at all?

AFAIK (subject to verification) pills made or distributed in the US must bear markings of some kind/type for identification purposes in the event of an emergency, tampering, recall, etc. This may be as little as a number or letter.

FAQ: Pill Identification

Was this from a local pharmacy or someplace else?

Doc

Drugs.com has a detailed explanation about drug
Imprints. All OTC and drugs must be imprinted by law.

Tablets not imprinted may be fakes or vitamins.
If you received this .. Report it. If the original
Rx was for placebo as per the doctor, then something
Benign might be it. Or if a patient's family gave you that
Pill, they may have swapped out the real narcotic and
Kept it for themselves.