Number 0 (zero) as it is a plain box and you can request any text / number you want on the box in the appropriate font for the era.
An empty reproduction box for the 1997 series Matchbox Superfast models. We reference this as the 'O' style.
This listing is for a standard or generic O style box with custom text on the end flaps to suit your model.
The images feature examples of this box. Really suits your Code 3 Custom models.