Harrison County West Virginia Mineral Rights Lease

Lately I've been getting a lot of interest in one tract in particular. It's a 50 acre tract in the Ten Mile District of Harrison County, West Virginia. The thing with this parcel is, I was told by the people earlier in my chain of title that I owned a full 100% interest. But, 5 years ago I signed a lease w/ Chesapeake & their landman said I owned only 50%. Now that their lease is due to expire in a week I have offers well beyond what 25 net acres should fetch, approaching $3,000.00 per acre w/ 17% royalty. Is there any way I might own more than the 50% I was told? And, is there also a chance my acreage is more than the 50 acres? What if I sign a new lease which says I only have 1/2 of 50 acres and when they get title certified it turns out my interest &/or acreage is greater?