Kavikanth Mahapatra, Bastian Schmandt and Carlos Araujo Queiroz, Thank you for your responses. I had found the unit stoc in unsolved example in a Fluid Mechanics Text book. It dealt with stoc as unit for flow rate of H2 gas. I needed to convert that into SI units to solve the problem. It is for sure a unit of flow rate.
Considering your last comment, it seems that "Stoc" may actually stand for "standard operating conditions", this being usually understood as indicating that the flow rate refers to a temperature of 70 °F (21 °C); and to the normal (or standard) atmospheric pressure (101.3 kPa).