I did a quick google search for "016503 rpm shaft" and got the pdf linked below: 

http://www.boschrexroth.com/country_units/america/canada/en/products/technology_areas/compu-spread/technical_documents/230_controller/6C_CS230_Automatic_Controller.pdf

Search that document for "016503"

A google search for "16503 conveyor sensor" get a number of hits I didn't look at.  I hope something there helps.

Gary