Theres some good advice and sme not so good advice so far.
Here are some issues that older weavers have.
The glass lenses MIGHT yellow up on some of the older scopes.
The scope might rust because its constructed from steel.
I do notice differences in clarity and light transmission verses my Leupold VX's and my Bushnell 3200's, but I do a TON of shooting at/past dusk, and this is where I notice the differences.
In my humble opinion your gonna spend at least 250 bucks to get a scope that is noticably better than what you have already, assuming it is in as good of shape as you say it is.
If it were me, Id wrap it in an old flannel shirt and put it up for now. Its not costing you anything to keep it, and what money you would get from it is not going to take a big chunk out of the cost of the better scope. Shoot, you never know when you might need a new scope for calling gun, a good 4X is never a bad choice no matter how old it is.
Hope that helped.