The ATMs or variable value stamps are issued with special machines; From a gummed or self adhesive paper, this machines print in the act the face value and other information.

There are two main types of machines ; The franking balances and the ATM self service vending machines. The balances are used by postal clerks in the postal windows inside the Post Offices; Depending on the weight, destination and the method of shipment, the balance issues an ATM with the correct value. It also issues a receipt for the purchase. Franking balance model EPELSA ET-CB used until December 2001 in Spain and Andorra Post Offices

SPAIN. Post Office equipped with franking balances EPELSA ET-RL, connected to the main postal computer system IRIS. The equipment is composed of the franking balance (to weigh, issue ATMs and receipts), the computer system and the printer for the registered shipments voucher.

In many countries these machines have been replacing or complementing the old vending machines of coil stamps and similar items, offering a better service to the consumer. These incorporate a computer system and a printing mechanism, and allows to the user to obtain a stamp or ATM with any face value wished at any hour. ATM distributor Model TERO from CIRILO AYLING SAIC used in trial period in Argentina

Around the world there are different manufacturers and models of ATM machines known include the German Klüssendorf (now disappeared) and Swiss Frama. Each kind of machine uses and issues its own style of ATM.

In Spain machines of type Klüssendorf, Frama and Mobba have been used, although nowadays all the current machines in the Post Offices are franking balances of the Spanish manufacturer Epelsa. From May 2003 there are also ATM vending machines from the same company.