These are the five most common terminal signs on the Indus Valley seals according to Iravatham Mahadevan's analysis (1982:316).
The first sign (from the left), the most common in the Indus script (10% of all known signs), is read by him as denoting a jar or sacrificial vessel (Sanskrit equivalent Sata) and probably denotes the concept of a priest.
He understands the second as denoting a lance or spear (Sanskrit equivalent Salya) and suggests that as a terminal sign it designates a warrior at the end of names.
The center sign he thinks refers to a bearer (Sanskrit equivalent Vahana) as in office holder or functionary; he notes that in old Tamil ministers and senior officers are known literally as "yoke bearers" (kaviti).
The fourth sign, which the unicorn seal being discussed here ends with, is read by him as a compound of the first and third, jar and bearer (Sanskrit equivalent Satavahana), and probably denotes an officer with priestly duties.
The fifth sign is read as a compound of the second and third, lance and bearer (Sanskrit equivalent Salyavahana), and probably denotes an officer with military duties.