Is it permissible for a company to issue a deferred merchandise purchase voucher where the buyer pays its price in advance in exchange for a price discount upon delivery, and is this considered a type of usury?

This transaction is called "Salam sale" (forward buying) and for its validity, the following conditions are required: specifying the characteristics of the sold commodity that affect its price, determining the price of the cars and the discount, and delivering the full price at the contracting session. In the described scenario, both conditions are violated because the buyer does not know the number of cars, their characteristics, or their price accurately at the time of the contract, which renders the contract void due to the presence of jahalah (ignorance/ambiguity). The Fiqh Encyclopedia and the scholars of the Permanent Committee have emphasized the necessity of knowing the genus, type, characteristic, and quantity of the musallam fihi (the object of the Salam contract) to remove the jahalah that invalidates the contract. If the contract was concluded in this manner, it must be rescinded and corrected if possible.