Is the work of my brother, as assistant secretary in the pawnbrokers of gold, where he estimates the value of the pawned item and takes one dinar for every 100 dinars, lawful or unlawful? And is the known fee imposed by the pawnbrokers upon the retrieval of the pawned item considered usury (riba)?

If the employee's job is to seize, appraise, and store pledges for a specialized entity, then the salary he receives is permissible (halal (definition)), as long as it is authorized or provided by that entity. This is because it is in exchange for a permissible (mubah (definition)) act. Scholars have permitted the pledge to be in the hand of a person agreed upon by both parties, and the cost of storing the pledge and the custodian's fee are borne by the mortgagee (the one who receives the pledge).