The gun was designed in 1865 as a broadside gun for ironclad ships and harbour seafront defence. A total of 190 were made. The gun was last fired in 1903.. This gun was first mounted in Halifax Nova Scotia until 1878, then at Bermuda until 1881 and then at Sheerness England until 1885. It was mounted at Middle North Battery Simon's Town in 1896 where it still exists.The gun, carriage, slide and mounting were restored in the East Dockyard Gun Shop in 1984. 9 inch bore(228.6mm) gun manufactured in 1855/1856. Muzzle loading gun. Barrel is rifled with 6 grooves, the only gun manufactured with this number of grooves. 9 inch shells had 6 rectangular lead protrusions that engaged with the barrel grooves to impart spin and thus stabilise the shell during flight. Cast steel gun barrel (Mk1) with wrought iron forged breech piece, cascable and trunnion, supported on fabricated steel gun carriage, slide and mounting.
FIRING SCHEDULE 2018:
21 February     12H00 (Armed Forces Day)
27 April        12H00 (Freedom Day)
08 May          12H00 (International Museum Day)
16 June         12H00 (Youth Day)
18 July         12H00 (Mandela Day)
24 September    12H00 (Heritage Day)
11 November     11H00 (Armistice Day)
16 December     12H00 (Day of Reconciliation)
 
It was declared a National Monument under old NMC legislation on 17 March 1989.
Geolocation
-34° 10' 51.6", 18° 23' 6"
References

https://www.simonstown.org/9%20inch%20rml.html