In the case of any sheep stock in which the number of ewes or the number of lambs sold off the hill at the autumn sales during the preceding 3 years has been less than half the total number of ewes or of lambs sold, the 3-year average price for ewes or the 3-year average price for lambs, as the case may be, shall, in lieu of being ascertained by the valuer as aforesaid, be determined by the Land Court on the application of the parties; and the Land Court shall determine such prices by reference to the prices realised at such sales for ewes and for lambs respectively from similar stocks kept in the same district and under similar conditions.