Inspect the parts and see if you can find anything wrong with them.
So many people selling parts kits are just re-packaging the parts from another company. There are some considered better than others and opinions vary on that. As well, with shortages for the LPK's right now, companies may be switching suppliers are getting the parts anywhere you can find them.
DPMS is one that people comment poorly and well on, seems like they are hit or miss, maybe they switch suppliers and get parts wherever they can find them. The package NOT showing any identifying marks is also suspicious its just a collection of parts from anywhere.
Given the current climate, unless you paid an extremely high price, you might want to just check the parts for any imperfections and if they look good use them, replace any bad parts later when the panic dies down. LPK's are hard to find. OR you could sell it on Gunbroker.com and probably make a profit.