Springbank 15 Years is a sherry matured expression. The distillery tasting notes seem to indicate a lot of Oloroso character, but I found it hard to get this. majbe they are relying mostly on refill casks.

Springbank 15 yo (46%, OB 2015)

Nose: even more mineral than the 10 or 12. Wet chalk, aspirin, graphite, some metallic touches. Light hints of antiseptics. Very flinty and austere with some coastal hints as well. Leather. Over time it moves towards light toffee and almonds. Mouth: oily, almost entirely on mineral notes, with an overpowering bitterness. Walnuts, grapefruit skin, quinine, herbal...