The cache is not at the posted co-ordinates, which are at the site of one of several capped wellheads in the Comiston area.
In order to find the cache, you will need to complete the Adventure Lab called Edinburgh's Water and collect the numbers from each location. You will have read there about the Comiston spring house which collected water from various springs and these were piped to the Castlehill Reservoir. My children attended Comiston Primary School, which is no more but was on the site of the nearby Pentland Primary School and the school badge depicted the four animals inside the collecting house which marked the location of each spring.
This is the best photo I can find of the Comiston School badge.
A number of years ago, I saw inside the Comiston spring collection house on a Doors Open Day. There were some information boards at the time which said that when the water was allowed to flow along the expensively newly-laid pipes to Castlehill, it did not work and the Dutch engineer, Peter Brauss, who was responsible for laying the pipes, fled the country, never to be heard of again! It was later discovered by his assistant that the problem was an airlock in the pipes and the water then started flowing. I can't find anything online to substantiate this.
The cache is located at N 55° 54.ABC W 3° 13.DBE
Listen at the door to the running water!
Congratulations to Peedieduchess for a very quick FTF.