The best I've come up with is a few proxies, like their deployment process. Someone doing continuous or frequent deployments probably have pretty decent code quality. A company that takes several weeks, several rounds of QA and a dozen release documents that need to be signed in triplicate, they have that process because they've been burned and need scapegoats when the inevitable happens.

The best part is that most people at companies like this aren't aware that it's not normal, so they'll be open about it.