As Industrial Control Systems (ICS) and standard IT networks are becoming one heterogeneous entity, there has been an increasing effort in adjusting common security tools and methodologies to fit the industrial environment. Fingerprinting of industrial devices is still an unexplored research field. In this paper we provide an overview of standard device fingerprinting techniques and an assessment on the application feasibility in ICS infrastructures. We identify challenges that fingerprinting has to face and mechanisms to be used to obtain reliable results. Finally, we provide guidelines for implementing reliable ICS fingerprinters.