General Motors GM EMD G-26 Diesel Electric Train Engine (Retiro Station, Buenos Aires)
LSM stands for Línea San Martín (the company operating this line).
Raúl Alejandro Rodríguez wrote:
This is General Motors GM EMD G-26 ex Croatian railways. In 2009 were acquired two of them #1000 and #1001 but see limited service on the line. Today I don't know where are both locomotives as all the line are run with new Chinese locomotives CSR SDD7.
For more info about the GM EMD G-26 locomotive, read en.wikipedia.org/wiki/EMD_G26.