This controls the display of the 'add to basket' region of the product. The valid values are:

• 'dropdown' - a select menu numbered from 1 upwards (to a number set in frontend.basket.addtobasketdropdown.max) displays just in front of the 'add' button so a customer can select a quantity and then add that number of items to the basket; this is most appropriate where users will only ever purchase a small number of similar items.
  
  
• 'textbox' - a free text field where the customer can enter a quantity and then click 'add'.
  
  
• 'none' - no quantity selection, just an 'add' button which adds a single item to the basket; this is most appropriate for big ticket items or customizable items where a customer is only ever likely to order one.

It should be noted that a customer can still edit the quantity of items as free text within the basket page, or click multiple times to add further items, so this setting does not create any limitation on what a user can checkout with.

Where no value is entered, the product will default to use the frontend.basket.addtobasketdisplay config setting value. So you should set that to act globally on your store, and then use this object config value on a per product basis to override it for particular items if desired.