Whilst using the Harvey's 'Skye - The Cuillin' map, I've noticed some small printed numbers on the sheet, the significance of which I don't understand.
Four examples are as follows:
At GR 502253 - the number '55'
At GR 503260 - the number '54'
At GR 537217 - the number '51'
At GR 538220 - the number '52'
The first two of these are near the hill 'Marsco'; the second two near 'Bla Bheinn' - but they're all definitely not spot heights, and I can't find any reference to them on the map legend.
Does anybody know to what these numbers refer?