[chrismorgan]

Eww, only 0.5 Hz tuning accuracy on that 440 Hz? That’s two cents (2⁄100 of a semitone). As an amateur with a not-terribly-high-quality piano I’d be ashamed to tune it two cents off; you really want to get within one (and you need the difference between same-pitched strings to be a good deal finer than that). I’d expect less than half a cent from a professional tuner on a decent-quality piano.

Unless the spec goes into more restrictive detail, you could tune a piano’s A440 honky tonky (roughly: one string 439.5 Hz, one string 440.5 Hz) and still be ISO-16:1975–compliant.