Yet another FB Marketplace purchase
Yes, it is a bumper. It is there to reduce damage caused by collisions. Class rules specify the size and material that the bumper is to be made of. The cork is pretty old and is OK for vintage racing but, if someone got picky, most classes these days specify that the bumper be made of some elastomer material. I have seen champagne corks and squash balls used on some old boats with sharply pointed bows.