True, but for the most part, RSA keys are the only keys that anyone encounters that start with long SEQUENCEs requiring two-byte lengths.

`eY` could be any JSON, but it's most likely going to be a JWT.

Neither is a perfect signal, but contextually is more likely correct than not.

That depends on the kind of abyss you are staring into. Mine had plenty of non-RSA keys, certificates (which are of course two-byte length all the time) and CMS containers.