You may try reaching out to some of the land devices companies that have been in midland for decades. They may be able to help. Shaw interests or doug furgeson or landsmith, might be able to help you out!
Caroline,
Waterson Calhoun, of Crest Engineering Services, did a historical valuation for Martin Co. royalty property I inherited in 1976. Contact info:
W. Waterson Calhoun, P.E.
Caroline, are you trying to value it now or at time of inheritance?
If from inheritance, was it producing, non producing but leased, or not leased?
I have often seen where value might be $10 for all non leased lands, if leased recently but not yet drilled, might be the amount of the bonus payment, and if producing it is a multiple of the cash flow.
Now if it was subject to an estate tax return, there should be a back up schedule supporting the value the executor used.