Mini Anderson Bailer. Auto suction bailer for a small dinghy such as the Standard Spindrift models, Amanda or Catspaw.
For a video of how we install this type bailer watch this video (small bailer used in video but method is the same for large bailer) https://youtu.be/3i7OUnkmGsc?t=808
Flange size - 56 x 92mm (2 1/4" x 3 5/8")
Fitting hole - 38 x 73mm (1 1/2" x 2 7/8")