I have 4 Sacagawea dollars from both 2000 and 2001. We've had them for years. 2 of them have always been different, but never researched until I recently started learning about coins and errors. I had read that there were a few done with experimental alloys and some with experimental rinses. I'm wondering if the 2 I have fall into that category of experimental coins. One is brown (thinking that might be a rinse error). The other is a yellow gold flat color and that one looks very different from a rim perspective, so am wondering if it might be an alloy error. Any help or guidance is appreciated. I am attaching photos.