A "seal" is similar to a coin with a design engraved on it, used to imprint melted wax. The "cord" was put through the seal so the owner could wear it around his neck. A staff was long wooden stick that helped in walking over rough ground.
This is a polite way of saying that he had sexual relations with Hagar. See how you translated a similar phrase in [Genesis 16:2](../16/02.md). (See: [[rc://en/ta/man/jit/figs-euphemism]])