I should mention that the birdcage piano I tuned is not really ancient. It's around 1915 I'd say. I do take the point that a really old fine quality grand would need to be approached with caution respecting what pitch to bring it up to. I'm not sure how I'd find out what pitch the birdcage in question was originally at. English upright piano-making at the time still had a large "cottage industry" segment with lots of small workshops turning out cheap parlour pianos, made down to a price. Whether the various workshops tuned to different pitches, I don't know. Need to check Cyril Erlich's book and see what he says! Best, David.
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