So how to tell a used btc miner has been miss used and damaged by previous owner.
Well does it work to spec when you get it.
What return policy does the seller have?
Buying used gear is risky if you pay with btc or any crypto maybe they will give a 1 or 2 day return policy.
So hope it works well use a seller that has a good rep.
I am not selling any gear at the moment i have a good rep but if I sell a used s9 I only give the buyer 2 days to check it out . Most sellers of used gear do not give a warranty.
If they sell here on bitcointalk.org you can read their trust.
This shows my business deals
https://bitcointalk.org/index.php?action=trust;u=64507it is very good one of the best on this site.
As I said I am not selling to you or anyone at the moment I am simply showing you ways to check on people .