Inchkeith Island was the principal component of the Outer Defence Line covering the entrance to the Firth of Forth.
In 1902 Inchkeith Island had four batteries, similar to those in 1911 as shown below. The Island has four machine guns for local defence.
By 1911 there were four batteries on the Island, as follows:
A single 9.2-inch BL Mark I. Initial plans were to mount two 9.2-inch, Mark 10 guns but this was reduced to one.
Two 6-inch BL Mark VI. The recommendation was to withdraw on these guns and add two 6-inch Mark VII guns.
Two 6-inch BL Mark VII.
A single 4.7-inch Q.F. gun that was identified for removal without replacement.
There are a number of YouTube Videos covering Inchkeith Island. The best drone footage located is shown on the attached clip by Scotland from the Sky.