This is a heavy die casting. Appears to be half of a front grille for a car. There is a place for a medallion at what would be the center of the two piece grille. My guess is it is from the late 30's or early 40's based on it's construction. I think it is upside down in the picture.
1956 New Yorker. You do have it upside down. Inspector @squirrel must have been working on the LaSalle; he's usually first to identify the unknown.
For once (perhaps the first time in history???) someone beat Jim (squirrel) to an identification. Way to go Ebbsspeed.
I'm going to stick my neck out and go on the record as saying......... that's the right side, passenger side half.