Correo Argentino’s 2026 UPAEP “Lagos & Lagunas” issue comprises two stamps showing Lake Nahuel Huapi and Laguna del Diamante. The postal operator gives the issue date as 22 April 2026. Both designs include the UPAEP logo and details printed in silver ink.

Nahuel Huapi is identified with its national park in Río Negro and Neuquén, while Laguna del Diamante is identified with Mendoza. The stamps measure 67 × 28 mm and were issued in sheets of 16 with illustrated sheet margins. A Mendoza government report published on 24 May subsequently highlighted the Laguna del Diamante design.