If the appraisal was done competently, the value for the 19 acres should have figured the acreage at a per acre amount based on the comparable 10 acre properties. If the appraisal property accounts for the acreage at a per acre price and the has the house appraised properly, that appraisal should be used as the inherited basis figure because it is closest to the date of death.

If the appraisal somehow only valued 10 acres or has other inaccuracies, you may need to try and combine that appraisal with the fair market value of the property for the county tax assessment to come up with a reasonable estimate of the value on the date of death.

You may want to consult with real estate appraisers and/or realtors about market conditions between the date of death and the date of sale. If you can develop documentation that the value would not have changed in those years, the FMA would have a stronger position to be used as fair market value and basis. However, more than a year between the death and FMA make treating the FMA as the inherited basis problematic.