Need some expert advise pricing my reefer trailer for sale.

I was needing some expert advise on what the price value would be on my box reefer trailer. I cant tell you the year my sister said it is a 53'. it was my grandma's trailer that she used for storage. I'm 38 and the trailer has belonged to my grandparents for as long as I can remember, the condition of the trailer overall as far as being used for storage is ok. As far as a working trailer not likely to happen. The side door would need to be replaced other than that the inside of the trailer is solid. Works great just being used as a storage container doesn't leak, keeps a cool temperature inside year around even with the piece of tin I use covering side door. With it being good for storage use only and in the condition it is in what price range realistically should I sell it for? Thanks in advance for any and all replies.