I assume you're already aware, but Rust hit 1.0 in May 2015. The further back before that, the less it resembled the Rust we have today; there were some major differences in early Rust (green threads, a heap-pointer operator, etc.). I don't think it's a stretch to say that no Rust job today actually requires Rust experience that dates back further than 1.0, and any job description that requires that likely was written by someone who doesn't know what they're talking about.