Your doubt is "well founded" The 1300 Series comes in two versions. One with Integrated Antennas and one with RP-TNC type connectors for external antennas. Neither model has both Internal and External Antennas;
The Cisco Aironet 1300 Series with integrated antenna can be quickly installed to provide a LAN bridge to a remote site or multiple sites. The 1300 Series with antenna connectors supports a variety of Cisco 2.4-GHz antennas, providing range and coverage versatility.