Question: Is it permissible to sell goods if we have them in posession before payment, but have some problems in describing goods (see above).
Answer: It is enough to point out the essential characteristics of the goods, and upon reception the buyer has the option to return the goods if he did not like it at first sight. You mention the number of items if it is sold by item, the size if it sold by size, the weight if by weight. You also mention what is usually considered as important features and qualitities. You don't have to go beyond that.
... and Allah knows best.