(petitioners, married couple, contributed permanent conservation easement in historic preservation facade on NYC townhouse that is designated as certified historic structure; appraiser estimated pre-easement value of property at $2.6 million and that easement reduced value by $290,000; IRS disallowed charitable contribution deduction for petitioner's failure to establish easement's value on basis that appraisal not qualified appraisal for lacking a valuation method; market data approach used to determine "before" value, but appraiser could not "properly estimate" resulting loss in value due to lack of data for comparable properties; court upheld IRS disallowance on basis that appraisal did not include specific basis for value under Treas. Reg. Sec. 1.170A-13; petitioners already barred from altering property under NYC law without approval from Landmarks Preservation Commission).