The only difference between the A600 and the A600HD was the addition of a 2.5" IDE Hard Drive as standard. The size of the HD was initially 20MB, but probably varied by country and may been subsequently increased to 40MB or 80MB. A600's without the HD designation were often sold pre-fitted with hard drives.
You may have noticed the 'PCI' branding in some of the photos, 'PCI Componentes da Amazonia S/A' was an authorised distributor in Brazil of Commodore Electronics USA. For additional information please see this image.