Why, I have attached a copy of the tuning chart for the Faventia barrel
piano. The low A is 217 Hz. The piano is tuned to A-435.
I have "restored" mine to the extent possible. I was lucky that the
pin block was still good. I did replace pins and put on new strings,
having the bass strings wound by Schaff to match the originals. Whether
you need new strings or not can only be told by listening and looking.
If they are rusted and corroded, replace them.
Even with new strings, that small sound board is not going to give you
much bass response, so don't expect one. If you can bring it to pitch,
and actually hear the pitch, the strings on there might be okay. New
leather was put on the hammers where there was leather. As I recall,
that was the bottom half.
After all of this, do not expect a great sound. Wooden hammers on
metal strings with a small sound board does not produce a really
pleasant sound. However, when tuned it is fun to listen to. Out of
tune, it is horrific, as you noted.
Speaking of tuning, any good tuner will work. Once again, you are
not that concerned about overtones and false beats. I used my very,
very old Conn strobe tuner. However, any of those tuning apps on your
phone will work. I find the strobe better and less affected by weird
harmonics. My phone app, nTrack Tuner, seems to have a difficult
time locking onto the fundamental frequency when there are a lot of
harmonics, like string tones.
Hope this helps.
[ Faventia Tuning Chart
[ Faventia Tuning Chart, exposure adjusted