I go with front license plate bracket as well. (#5)
DING DING DING!!!! winner!!! bought it some time ago, it had period badges on it, so it looked pretty original to me. PA doesn't have a front plate requirement so I never went about cleaning it up or trying to figure out how it mounted.
Don't you spend part of every day looking at those anyway? Why would OUR parts hold any mystery for you at all?