 The class F locomotives were the only ones to be named by the GNSR, all other classes being numbered only.The class originally comprised eight locomotives, six built by the North British Locomotive Company in Glasgow in 1920, the remaining two by GNSR at Inverurie Works in 1921.The five locomotives ordered in 1898 that the GNSR was unable to pay for were offered for sale by Neilsons, with the authority of the GNSR.