I worked for the NHS/PHW a few years ago. We would get internal emails and such, occasionally from Wedinos.

It’s estimated, with the findings from Wedinos, that a great majority (over 70% a few years ago) of prescription pills, including Tramadol and Diazepam as the biggest culprits, were counterfeit and more or less generic Benzos.
They would be in blister packs, in proper looking packaging. All of that can and has been replicated, unfortunately.

If you want to see some public findings for yourself, check out wedinos.wales and what testing they have publicly available. People have been sending samples to them for a long time, and people who do this stuff frequently are likely to know about the service from various darknet communities (I don’t think it’s necessary nor responsible to mention them).

I would say it’s not worth getting these things from darknet marketplaces, as there’s a good chance you won’t be getting what you think you’re getting.