Let $(X,d)$ a metric space and $\bx = X \times \mathbb R$ denote the partially ordered set of generalized formal balls in $X$. We investigate the relations between the Martin topology and the product topology of certain topologies of $X$ and the Sorgenfrey line. We give a condition that the Martin topology coincides with the product topology of a metric topology and the Sorgenfrey topology, and consider on the conditions that the Martin topology is homeomorphic to the product topology of a metric topology and the Sorgenfrey topology. We also show that the space of formal balls on $\mathbb R$ with the Martin topology is homeomorphic to the square of the Sorgenfrey lines.