Final answer:
The pocket-sized form designed for immediate purchases and payments, typically used in the field, is the Standard Form 44 (SF 44).
Step-by-step explanation:
The multipurpose pocket-sized purchase order form designed for on-the-spot, over-the-counter purchases is known as a Standard Form 44 (SF 44). This form acts as a combined purchase order, receiving report, and voucher for payments of supplies and services.
The SF 44 is primarily used in situations where it is expedient to purchase supplies or services immediately, and it is designed for field use or when immediate delivery is required with payment to be made on the spot.