Until the 19th century, there was no coordinated effort to standardize musical pitch, and the levels across Europe varied widely. Concert pitch was standardized at A=440Hz only as late as 1955.
Skipping all the intricate historical details, in the 19th century a wide variety of pitches was still in use ranging from A=426 up to A=458 Hz with the most commonly used pitches around 435 (pitch in Paris was standardized at A=435 Hz in Feb. 1859; before that date opara houses and concert halls even within Paris tuned to different concert pitches) and 451 Hz (London, Lille, Belgian army, Milano, Berlin). It made of course no sense to build saxophones for all the different subtle pitch varieties, but a low pitch and a high pitch variety were respected. I came across a number of 19th century intruments that were indeed build for high pitch. High pitch instruments were even built as late as 1960, as a Dolnet baritone from that year taught me.
The most obvious sign of an high pitch instrument is its unwillingness to play the bell notes 'in tune': they are easily about 30 cents to a semitone sharp according to modern standards. At the same time, notes played on short tube lenghts tend to be flat. But there is a far better way to find out: compare notes played on a great length of tune of the instrument with the same notes played on a short length.
Say, you finger a low B, C and C# but play these three notes an octave higher in the middle range. Next you play the same notes, this time using the normal fingering. You can hardly influence tuning levels of the notes played on the great lengths with either mouthpiece position or embouchure. But with mouthpiece position you can decisively change tuning levels of notes played on the short lengths. Next you tune your mouthpiece to such a position that notes played an octave higher on a great length match as well as possible the same notes played on a short length. A perfect match will not exist, but make it as well as possible for all three notes, allowing for some sharpness in the 'long' versions of the note. Now your instrument is in balance with itself. Only now will you be able to check for which pitch the instrument was build. And most likely it will play far better in tune now, than when forced to play at the levels indicated by a tuning device.
By the way, you can fairly safely use this technique of tuning for a modern instrument and be sure that you will reach a nice general level of tuning witout the use of a fork or electronic device.
Compare with a modern instrument! Do not pay attention to the length of the neck: truncated cone length has changed through time, certainly for sopranos. It is the spacing of tone holes that will tell you the story, as shown below; Buffet-Crampon S1 versus Royet:
You have to be a little bit careful in comparing the curved instruments, though, as the difference in spacing is not quite visible in their straight parts.