coerce-to-objc-class returns the Objective-C class pointer for the class specified by class. If class is a string, then the registered Objective-C class pointer is found. Otherwise class should be a foreign pointer of type objc-class and is returned unchanged.
This is the opposite operation to the function objc-class-name.
LispWorks Objective-C and Cocoa Interface User Guide and Reference Manual - 15 Feb 2015