This is an appeal by the assessors from a decision of the Appellate Tax Board granting a partial abatement of a real estate tax. On July 13, 1966, Costin purchased for $115,000 a large tract of land in Nahant with certain buildings on part of it. Portions of the land were sold by Costin on or prior to October 3, 1966, for $62,500, in the aggregate. As of January 1, 1967, Costin owned three lots containing a total of 170,407 square feet of land on which stood a large one family frame dwelling 100 years old (which could be found to have incurred “a considerable amount of functional obsolescence”), a greenhouse, a swimming pool, and a cabana. This property was assessed on that date for $70,600. After denial of an application for abatement, the assessment upon Costin’s appeal under the formal procedure was reduced by the Appellate Tax Board to $55,000. This amount was $2,500 more than the purchase price ($115,000) of the area bought by Costin less the aggregate of *727the sales .prices received by him for the land sold by him in 1966 ($62,500). The board’s conclusion was based upon adequate subsidiary findings which in turn were supported by substantial evidence. The board was not required to accept the opinion expressed, or the valuation principles used, by an expert witness called by the assessors.

Decision of the Appellate Tax Board affirmed.

The taxpayer is to have costs before the board and in this court.