An item from my own personal collection, purchased when originally released in 1989, this has been stored away for many years. 
I noticed when other sellers were selling this item that they all seem to have the same fault, a deterioration in the material used for the "rubber" suit and cape, which starts to flake off and crack over time, resulting in bits of black inside the box and on the box window where it touches the costume.
As a result, I looked at my own figure and found the same had happened. To show the full effect of this, I opened the box to photograph the figure to sell it, so the buyer can see for themselves the condition it is in.
To be fair, this one is in better shape than most I have seen advertised, probably because until now it was unopened.
There may be a way to stop this deterioration, but to be honest I don't have the time or the patience to look into it, and have decided to sell the figure as is. 
As I have fully described this condition, I will not be accepting returns on this item as "NOT AS DESCRIBED".