Typically, the center clamp in the front bumper has vibrated loose and is gone. A poor design to secure it to the bumper bars: in the center where the most flex would be. Had the backing plate been longer and been furnished "ears" to hook over the bumper bars, chances are that so many of these clamps would not have fallen off. Look at photos of well-worn Model A's from the late 30's and into the 1950's and very often that center clamp is missing. How much more money would it have cost Ford to extend that backing plate this way, three cents per car? Add that to the dealer price and keep owners happy.
Following up on the nit-picking topic, I find it fascinating to look at these pictures and see the wide range of ingenuity, resourcefulness and imagination humans can come up with to make their old jalopies roadworthy and still usable. No two such survivors seem to be exactly the same, although there are some recurring commonalities. I love finding abandoned Model A and T Fords in barns, ravines and on the "back 40" and see what changes people had made to them over the years in order to squeeze a few more miles out of them or make them distinctive from the other 5,000,000 Model A's on the road. Human adaptiveness is a bottomless pool.
Marshall