This multi/offset is located at Johnston War Memorial Park. As the name would imply, you will be visiting two spots of note in the park, with one stop being a pavillion and the other a bridge.
Locate a an engraved plaque near the base of the pavillion. Take note of Thomas and Anthony's last name.
Locate a mounted plaque on a tall piece of wood near the bridge. Take note of Nina's last name.
To get the cache coordinates, input the last name from the pavillion stage followed by the last name from the bridge stage.
The Certitude keyword will be these two last names in the order of pavillion then bridge. Correctly inputting these two names into Certitude will reveal the coordinates and hint for the cache, which is located near the bridge stage. Hope you enjoy.
You can validate your puzzle solution with
certitude.