The Image Key
The Image key that COMInterfaceImp class>>register creates in the registry is used by the generic in-process stub (IPDolphin.DLL) to specify the path of the image which contains the component implementation. This is possible because after COM has loaded an in-process DLL, its first call into that DLL passes the CLSID of the required component. With knowledge of the CLSID of the desired component IPDolphin.DLL can look up the required image from the registry and load it. With the registry entries listed above (as created by evaluating COMInterfaceImp class>>register) one's working development image will be used.
If the Image key is not present, then the image must be bound to the DLL, which is the form used for deployed DLLs.