How do I remove this Schlage double-cylinder deadbolt with no visible screws?
Those are just metal "caps" that push into the screw heads..  

The screws are located under those metal "pins"
The metal pins are actually screws that have metal caps pushed into them so they look like you can't unscrew them.  Take a very sharp small screw driver and pry under those caps and they will pop off revealing the screw head.

See here:
https://www.youtube.com/watch?v=kxtUFCHXBF0