Fullarton estate is one of the oldest parts of Troon, and was originally known as Corsbie or Crosbie until the Fowlertoun or Fullarton family moved there from Irvine. The two oldest remaining buildings from this area are Crosbie Kirk (marked on the oldest Troon maps from 1608) and Crosbie Keep whiuch is now known as the Old Ice House. The tower or fortalice became a ruin after the building of Fullarton House (now demolished this stood where the car park is now) in 1745.
A charter dated 13th April 1344 grants Sir Adam of Fowlertoun "the lands of Foulertoun and of Gaylis (Gailes) in Kyle-Stewart... together with the whole fishing from the land which is called Trune to the entrance of the harbour of Irewyne (Irvine)". Certainly by 1493 George Fullarton was known as the Laird of Corsbie and so must have been living at the keep there. He obtained a charter from James III on 24h October 1464 "of the lands of Fowlertoun, Marrass, Shewalton, Harperland, and Western Laithis, also Corsbie, Trune, Craiksland, and Russelsland, all lying in the Bailliarie of Kyle, and Sheriffdom of Are"
To find the cache there is no need to disturb the ruined fortalice. Walk around the outside of it and stand with your back to the back wall at the point where there is a hole at ground level. Looking straight ahead note a large tree ahead but somewhat to the left.
There is a good sized car park in the woods by the picnic area.