If you don't specify the rank, the order will be handled as "all ranks" and a product with an arbitrary rank will be delivered. We cannot say which rank that will be.
In the case of zener diodes, if, for example, the rank classifications "B, B1, B2, B3" appear in the rank table, "B" is "all ranks" and includes the ranks of "B1, B2, B3". In this case, if there is no rank specification, the order is handled as "B" rank and a product with a rank of either "B1", "B2", or "B3" will be delivered.
The rank is shown on the packing label.
The rank is also indicated in the marking on the actual product, but the indication method differs depending on the product and package.