The cache is a bird-box, but unlike the hundreds of bird and bat boxes on the Nature Reserve, this one is for treasure hunters, not animals. The front of the box is hinged at the top and opens from the bottom as soon as you solve the puzzle. There is a disabled accessible wc behind the visitor centre. Disabled cachers may need to use this to help solve the puzzle.
Start from the Highland Titles Nature Reserve car park. To reach this, turn in off the A828 about 1 mile south of Duror. The entrance is just north of the Salachan Burn and easy to miss. Take care when you leave as the visibility is poor and traffic goes too fast!
Unfortunately there is very poor phone signal, but as there is free wifi from the visitor centre, you should be able to use that instead.
Enjoy.