Coins! They all have edges, and while some have text or stars, many are reeded. But why?
Reeding on a Morgan Dollar
When coins are milled, the blank is held between the two dies with a collar that fits almost exactly around it (at the US Mint, the collar is only 1/5000 of an inch wider than the diameter of the coin die). When the coin is struck, it flattens out and expands into grooves in the collar, creating a reeded edge.
A Belgian 5 francs as an example of filing in my collection.
The edge of the 5 franc originally had stars and text, note the remnants of three letters, and the horizontal lines made from filing.
Back in the days of gold and silver coinage, people came up with a side hustle everyone could do. The trick was to take a coin, file away the edge slightly, and then use it. When they had done this with enough coins, they would end up with a pile of precious metal shavings. In order to prevent this, reeding was introduced. It did not, however, always prevent filing.