This is a filter with one layer one side coating. How to distinguish a coating side?Let’s suppose the top side (green color) is the coating side and have a look at the red line as the above graph.
If you can not see the red line,we confirm the top side is the coating side.If you can see the red line,we confirm the top side is not the coating side.Let us presume the bottom side is the coating side.Then take the bottom side to the position of top side and observe the red line as the above to confirm the coating side.