It’s only weird for a boss to do this if his behaviour implied certain “expectations”. Otherwise it is a bonus for work well done. It happens all the time in certain industries.
A friend is a paralegal and has received a Tiffany ball bracelet, a trip for two to a private Caribbean island & a bottle of really old scotch because one of the lawyers at the firm knows that her husband is learning about aged whisky. Oh and also a Mont Blanc pen.