As for a guard for protecting your finger, I haven't really ever felt the need for that, but apparently the former owner of this gun did
This one had a piece of metal soldered in to place behind the trigger guard loop if you will. This gun has a Miller marked single trigger with the less often encountered rocker button selector just forward of the trigger versus the selector being on the safety slide.
I would believe this trigger was definitely installed by Miller since Ithaca was producing their own single trigger by this time.
Finger Guard
Threaded Mode