I have a leupold mark 4 3.5-10x40mm m1 scope in very good(optically perfect) condition with no ring marks. Sunshade included but with no box or paperwork. What would you expect to get for this if it were your own?

I'm not familiar with this particular scope and don't know how much demand there may be for it in the used market, but by and large, used Leupolds in excellent condition bring around 75- 80% of their retail price.

I have never worked out whether scopes keep up values the way houses and rifles can but everything loses value after it is first retailed.

A lot of shooters hang on to the scope when they sell a rifle it has been on and I've assumed this was because buyers don't want to pay for scopes at the percentage they will for s/h rifles.

Three-quarters of the present new discounted price could be something like it unless you wait and wait for a sucker to pay more.