So I've started taking a photo class at my highschool and one of my friends is lending me his old film SLR. This class is my first introduction to film photography. He's lent me a huge bucketload of stuff, with the camera being a Nikon FM2. There's also a filter, the kind of which I am clueless. I must be doing something wrong, because I'm not getting any answers on search engines. It's a Black's Coated 1A, 52 mm. When I look through it, the glass is tinted slightly pink. It screws on and fits on the 28mm Nikkor lens. Is it just a UV filter? I find that sort of redundant since the 28 mm already has a UV filter on it... any help finding out what it is/tips would be greatly appreciated. Thanks in advance!