The great thing about coin collecting is that you can't do it wrong. We all have different coins that strike our fancy and everybody's tastes are as unique as each collector.... So if those blue hued cents do it for you, then by all means... Build yourself a collection around them!
Welcome @Zelda. Toned coins are collected by many, but don't often demand much of a premium. Your photos don't do them justice, I'm sure. As for checking for anything on them, there is a large and small date 1970, But the value is in the S mint mark. The 1975, just a true Lincoln, meaning it ISN'T zinc. Something you may not be aware of, is posting photos Full Size so they are easier to view, so I'll send this: For the best results, you should post "in focus," FULL IMAGE photos (after you upload your photo, two buttons appear: Thumbnail and Full Image, click Full Image and your photo appears full size on your post and are easily enlarged by clicking on it). Photograph coins on neutral backgrounds like black, grey, or white. Crop out superfluous background so just the coin shows (you can use https://www.remove.bg for free), and post photos with correct orientation so members don't have to turn their computer in some awkward fashion to view it properly. While it isn’t always necessary, it is nice to show both the obverse and reverse, even if your question is just about one side. Members can often give more valuable information having both sides to evaluate. Add close ups of areas you have questions about and make your questions as definitive as possible so we know what you are asking for. And try to have the best lighting possible to show the most favorable photo of the coin. Hope this helps in the future. Good luck.
They were handled by someone with oily fingers. Over time they tone Coins are dirty and nasty. Make sure you properly wash your hands well after you do your searches. Worth? 1 Cent each IMHO
