Which of the items below is NOT disclosed on a customer confirmation?

The correct choice indicates that the fact a security is marginable is not disclosed on a customer confirmation. Customer confirmations are designed to provide detailed information about the specific transaction that has occurred. This includes the kind of transaction, whether it's an agency or principal transaction, and any associated costs like commissions or markups.

The marginability of a security, while an important aspect of trading, is typically not included on customer confirmations. This information is usually documented in other communications or regulatory texts rather than on a confirmation receipt, leaving customers to seek this information through their account agreements or other disclosures.

In contrast, the other items mentioned in the choices are directly related to the specific transactions and must be disclosed. For instance, when a member acts as a market maker, this information must be communicated to ensure transparency in how the order was handled. Similarly, in agency transactions, confirming the amount of commission charged is standard practice to maintain clarity between the broker and the client. The mark-up in riskless transactions also requires disclosure to inform clients of the costs associated with price movements on matched transactions.

Therefore, the focus on the need for clarity and transparency in transaction confirmations underscores why the marginability status is not part of what is typically outlined in customer confirmations.