Cache box was fired from cannon that is closer to camera. See attached photo. The cannon is located less than 300 metres from Coast Artillery Museum.
Data
Mass: 0,8 kg
True bearing: 290,9°
Angle (up from horizontal level): 52,8°
Initial velocity: 314 m/s
Gravity: 9,8 m/s²
Air temperature: -7 °C
Air resistance: None
For clarity's sake assume that the projectile lands at same altitude from where it left.
There are plenty of cannons in Suomenlinna. Try to shoot your own cache box from there. It's fun!
Other shots:
Cannonade from Suomenlinna #2
Cannonade from Suomenlinna #3