Calculate the normal force (N).

Since the object is on a horizontal surface, the normal force is equal to the weight of the object.
The weight ($W$) is given by $W = mg$, where $m$ is the mass and $g$ is the acceleration due to gravity ($9.8 \text{ m/s}^2$).

$$N = mg$$ $$N = 80 \text{ kg} \times 9.8 \text{ m/s}^2$$ $$N = 784 \text{ N}$$

The problem states that the object is pulled by a force of $500 \text{ N}$. For the object to be on the verge of moving (or if it's being pulled but not yet accelerating, implying it's at the maximum static friction), the applied force is equal to the maximum static friction force ($F_{s,max}$).

$$F_{s,max} = 500 \text{ N}$$

The formula for the maximum static friction force is $F_{s,max} = \mu_s N$.
We can rearrange this to solve for $\mu_s$:

$$\mu_s = \frac{F_{s,max}}{N}$$ $$\mu_s = \frac{500 \text{ N}}{784 \text{ N}}$$ $$\mu_s \approx 0.637755$$

Rounding to three significant figures:

$$\mu_s \approx 0.638$$

The coefficient of static friction is:

$$\text{0.638}$$