The aircraft in question range from a 1950 C150 to a 1982 C172. All have exactly the same annotations in the POH and in the UK Supplements (although they do not all have similar placards nor similar equipment).
Your suggestion that the equipment may have been added since manufactur is ceratinly plausible. If this were done in the UK, would there have been a requirement to change the placards?
FFF
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