Hi Erik and Pralhad,
Well I have being using these sensors for years togather, never faced any problems; and almost every company, manufacturing process control equipments, in Mumbai, is outsourcing these sensors from those proximity sensor manufacturers.
Atleast in this field of Proximity sensors, it is almost taken as a standard, that you buy any make of sensors (by specifying Supply voltage, diameter, and type of output) you will get a rugged proximity sensor. I know this because I happened to work for a process control equipment manufacturer, who is using (outsourcing) these sensors for almost 15~18 years. Never faced a single service call for faulty proximity sensor due to manufacturing defect.
And if you happen to be in India, visit the exhibitions of PlastIndia, ChemPlast, Pharmatech,etc., and you can get the above information from any of the technical person of process control equipment manufacturers that are taking part in the exhibitions.

As far as the contact numbers are concerned, I will post them within a day or two.


Thanks to all.
Mr. Kiran V. Sutar.