Although equal temperament became the standard temperament in the 18th century, unequal temperaments continued to exist until the early 19th century. Since subtle nuances were certainly known and taken into account in the tuning practice, a sensitive interpretation of such instructions seems to be advisable.
Taking Beethoven's Op. 34 as an example, Mark Lindley explains his method of interpretation. The article by Klaus-Jürgen Sachs provides a historico-analytical introduction while Conny Restle comments on Beethoven's pianofortes.

Preface
Klaus-Jürgen Sachs: Beethoven's Variations for Piano, Opus 34
Their place among his works
On the 'new Manier' in Opus 34
The overall concept
On the forms of the indidual settings
Klaus-Jürgen Sachs: About Key Characteristics
An outline of the problem
Interpretation of the evidence for Beethoven's position
Key characteristics in Beethoven's Opus 34? - Conny Restle: Beethoven and the Hammerklavier
Beehoven's pianofortes
The two pianofortes by Joseph Brodmann
Mark Lindley: Nuances of Intonation: Technical and Historical Background
Mark Lindley: Nuances of Intonation: Musical Effects
Appendix I: Mark Lindley: Extracts from Anton Schindler's "Biographie von Ludwig van Beethoven"
Appendix II: Mark Lindley: Advice for Tuning
Appendix IIIa: Klaus-Jürgen Sachs: Synoptic Reproduction of the Musical Score and Sketches
Appendix IIIb: Klaus-Jürgen Sachs: Facsimile of the Pges from the Wiehlorsky Sketchbook with Diplomatic Transcriptions
References
Index of Names
CD Tracks