Pick's Turf Register states Old Scarborough Mare was foaled 1715c, and beat the Duke of Rutland's Bonny Black. However, it appears the racing record of Bonny Black has been confused with races run by two other horses of the Duke of Rutland, Ebony (1714) and a mare by Basto (1715), with some of the races of these two mares erroneously being attributed to Bonny Black.
It appears Bonny Black raced between 1708 and 1713, so her race against Old Scarborough Mare must have occurred between those dates, dating the Old Scarborough Mare to 1705c, 10 years earlier than Pick's estimated foaling date. The race win was probably:-
April 1711 - King's Plate [mares] Newmarket (from Bonny Black)
She is grandam of significant sire Young Belgrade:- sire of 1) [Old] Standard - King's Plate winner 1742 and sire of top class racehorse Jason, winner of 7 King's Plates in 1754 and 1755; 2) [Wyvill's] Volunteer - King's Plate winner in 1742 and 1744; 3) Primate - King's Plate winner in 1746, 1748, 1749 and 1751; 4) Antelope - King's Plates winner in 1752; and of several successful broodmares.