A wholesaler who acts as an agent on behalf of the owner of the goods in buying or selling for a commission proportionate to the value of the transaction is...

In the context of trade and commerce, a wholesaler who acts on behalf of the owner of goods in buying or selling, and receives a commission based on the value of the transaction, is typically referred to as a factor.

Here's why:

A factor is a type of agent who is enthusiastically involved in the buying and selling process of goods. This role often involves taking possession of the merchandise, managing the sales, and sometimes providing advance payment to the owner. For these efforts, the factor earns a commission proportionate to the transaction value.

Factors differ from some other types of agents in that they often have more responsibilities, including the power to sell goods in their own name, collect proceeds from buyers, and handle various logistical aspects of the sale.

In contrast:

- A commissioned agent might not necessarily take possession of the goods or manage the detailed logistical aspects of sales.

- A del-credere agent provides a guarantee to the principal that the buyer will perform as agreed, essentially assuming responsibility for any buyer defaults, but this does not inherently describe their primary role in the wholesale process.

- A speculator doesn't fulfill an agency role for the owner of goods but rather buys goods directly to sell at a profit, often taking on significant risk in the hope of financial gain.

Therefore, in the scenario you provided, the term most accurately describing the wholesaler's role as an agent working for a commission based on the transaction value is a factor.