Which of the following is a possible observation of a customer that may indicate intoxication?

The observation of having glassy eyes and fumbling is a significant indicator of possible intoxication. Intoxication can affect a person's motor skills and vision, leading to physical signs such as impaired coordination, which is often evidenced by fumbling actions. The appearance of glassy eyes can also suggest a level of intoxication because alcohol consumption can cause changes in the eyes.

In contrast, speaking clearly and coherently, walking steadily, and being overly polite and reserved are not typically associated with signs of intoxication. These characteristics may indicate that a person is sober or may simply not be affected by alcohol at that moment. Being observant of behaviors like fumbling or having glassy eyes can therefore be crucial in assessing whether a customer may be intoxicated and needing intervention.