It appears to be some type of tab for locking something in place. On the backside edge there are remnants of where it pivoted and the male protruding pin would have locked into something indented, somewhere lol.
I'm picturing stamped sheetmetal parts - like a tall oil cap 1/4 turn locking into position, part of a baffle or brace in stamped rocker covers, heat stove pipes, air cleaner base, fan shroud.
It's likey NOT a mechanical part. You will know what it is when you need it and get further along with your cleaning...
