The Indus Dictionary Project
This is a stylised pictograph of an outflow water clock. The image depicts an open vessel with straight sides and the base set at right angles to the sides. A funnel on the side of the vessel allows water to leave at a steady rate. On the rear wall of the vessel are horizontal lines. The observer can compare the water level with the lines to determine how much time has passed.
Broken seal with the beginning of an inscription, found in structure number 3H (NB. The symbol is the mirror image of that seen on the seal.): Vasant Shinde, Toshiki Osada, Akinori Uesugi and Manmohan Kumar, 2008: A Report on Excavations at Farmana 2007 -08: Chapter IX, p.104, Figure 106: Indus Project, Research Institute for Humanity and Nature, Kyoto, Japan: https://www.academia.edu/37296726/A_Report_on_Excavations_at_Farmana_2007-08: Accessed: 28 June 2020.
It seems unlikely that the vessel would have been this shape. The shape, of the symbol, was probably chosen to indicate that a precise measure of water was needed to operate the clock.
Water Clock: Lynn Fawcett, 2020.