I have an interesting phenomena on an older Leupold scope that maybe somebody else has seen before and knows what it is.

I have centered the crosshairs, and I have focused them.

When I look at something in the distance, say 25 yards, or 50 yards, or even 100 yards (checked with Swarovski rangefinder) everything is very crisp and in focus from the edges to about 1/2 of the way to the center. From there everything is not crisp and is slightly out of focus all the way to the center where the crosshairs meet.

Any ideas what this might be?

Time to send it into Leupold. They will repair or replace it under their warranty for free. No sense trying to diagnose it yourself when they will fix it for you regardless.

Well that's an old old scope, I'd retire it and just buy a new Leupold. You can send it back and they will repair it but it will never have centered cross hairs unless you buy adjustable mounts...

I recommend you buy a good used Leupold with center reticle for $150.

All that said there have seen thousands of deer killed with scopes out of focus..I have seen newer scopes totally out of focus and the gun owners been killing deer and elk with them for several years.

You should see some of the scopes in the North Pole, Mexico, Alaska and on some USA ranches, Some of the scopes Ive seen used in Africa even by some PHs would scare ya to death but they are successfully used daily to provide meat for the table, and to keep big bad critters out of the garden..thats when I realized all you need is an X and a properly sighted in rifle, the rest is just mind gravey.