Need an estimate

Um, a photo would be really useful. You say it's only a 5 point star with a crown in the center. Then you suddenly start talking about a bayonet and rolling block. That tells us that we don't have the complete description to go from. Details are important. What is it made from? Plastic? Wood? Aluminum? How is it finished / colored? No markings at all on the back even? At a very (and I mean throw an idea to the wind) guess, based on what little info we have on it, you are looking at a wall medallion from either a manufacturing company (i.e. liquor such as 5 star whiskey) or a Military / Semi Military institution (i.e. military college fraternity, or military division logo). Depending on what you have, what it is made of etc. you are looking then at a price (again a dart lofted into the wind) of between $30 to $200 at a WAG!