The possible existence of Internal Labour Markets (ILMs) in the Spanish railway company MZA at the beginning of the Second Industrial Revolution is explored by means of non-linear Optimal Scaling techniques. The results show the presence of two characteristics of ILMs predicted by the theory: the existence of «ports of entry» for the employees of the company at low levels of qualification, and the presence of long-term labour relations. Thus, in common with recent studies on UK railway companies, we conclude that the company MZA operated some kind of ILM before the start of the 20th Century.
