https://www.mercadopago.com/mla/account/credentials

Modo Sandbox
Public key: TEST-a10a749f-0984-432b-a49e-f2e07c863b3d
Access token: TEST-5017160968049698-123011-721e22652099f276ab78fc6863b54b2d__LC_LB__-83750726

Modo Producción
Public key: APP_USR-3258e061-3e9a-4b58-8d4b-7df2a0bfc1a8
Access token: APP_USR-5017160968049698-123011-099fc55b6a76ef6b2659cde82533d218__LB_LA__-83750726