Aah - this is a potentially really important and musically valuable instrument so persist and don't lose courage.
It will be a Viennese action, so the hammers back to front, might be leather hammers rather than felt and clearly hasn't been maintained well in a while. It might have original strings and need restringing. If the original strings 390 might be the highest pitch to which you can tune. It's a pattern which was common, most famously to Streicher which was Brahms' favourite instrument, and I have a version made by Emerich Betsy for which there's quite a fan-club http://www.emerichbetsy.com/ and https://youtu.be/xwh4Xb1waC0?t=959 is my instrument in concert. The sound is rather fortepiano-ish from the player's position and quite a "modern" sound at right-angles where an audience might be.
Oblong tuning pins - it's important to have a lever which fits snugly and you might have to get one made or trawl old tools on ebay. Pins might be loose so be armed with CA.
Getting the action out involves removing the front rail. It slides out sublimely, dropping the back of the action frame but getting it back in is a pig, or a knack. It goes in and you might have to raise the front, and then when nearly in the back has to slide up a steep wedge. This might need candle wax, soap or talk to lubricate it. Having located where it's about to rise, a nudge from your hips might be necessary to push it in and the back up the slope.
The depressed note might be on account of being caught on a check so you are going to have to take out the action.
There's a good photo of what you might find on http://www.pianos.fr/en/mecanique-viennoise-392.html and another photo on https://www.worldpianonews.com/general/explainers/early-piano-actions-and-the-oeser/
From the video of the Emerich Betsy I hope that you'll be able to persuade your client as to the merits of properly engaging with the instrument and spending whatever it costs to get it into good order.
As you'll hear from the video these straight strung instruments respond really well to an unequal temperament and indeed their resonance relies on the tuning so do try Kellner as in the video.
Best wishes
David P
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David Pinnegar BSc ARCS
Hammerwood Park, East Grinstead, Sussex, UK
+44 1342 850594
"High Definition" Tuning
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Original Message:
Sent: 08-18-2023 12:18
From: Keith Roberts
Subject: 1860 trouble?
I just got a call about tuning and checking out this grand.
Anybody have some words of wisdom about what to watch for?