Good photos are mandatory if you want to sell them quickly and get top dollar. Show the scope itself, the condition of the glass, and the reticle. Just posting "...it's X manufacturer's 5$Lb-N reticle..." is not enough because accurate depictions of reticles can be hard to find.
Beyond that, I'd look through the threads selling scopes here and make sure you answer the most common questions: tube diameter, weight, finish, and other specifications. Describe any nicks, dings, ring marks, or other flaws, and have pictures of them specifically.
State where it was made if you know. There can be big differences in the value of scopes made in Country A vs. Country B.
Describe the eye box. You can list a figure in inches but it helps to say, "The eye box on this one is large/small/whatever."
I also describe the rifle(s) on which that the scope has been used. The fact that it's been on a 308 or 270 with no problem is very different the fact that it's been on a lightweight 416.
Okie John
