Because of the simplicity of the traverso’s construction, the knee-jerk reaction is to purchase any flute you come across. This is hardly the case! There are plenty of factors to keep in mind when shopping for a traverso.
First, it isn’t necessary to attempt to find an original 18th century instrument. It is rare to find an original flute from this time in good playing condition, or pitched to one of today’s more standard pitches. It’s much simpler to find good quality replica flutes—which will be pitched properly, and easier for a Baroque flute novice to play in tune with a consistent sound.
Next, the type of repertoire you’ll be playing the most often should inform your decision. Flutes modelled after Jean Hotteterre and Joannes Hyacynthus Rottenburgh, pitched at a=392, are especially suited to earlier French Baroque music. Instruments modelled after Johann Wilhelm Oberlander and Jakob Denner, pitched at a=415, are suitable for mid-18th century German flute music. Flutes modelled after Thomas Stanesby Junior, pitched at a=415, have an open sound which makes them particularly suited to music by G.F. Handel or other English baroque music. Those modelled after Godfridus Adrianus Rottenburgh, Carlo Palanca, Johann Joachim Quantz, and August Grenser are all good options if you are planning on playing a wide range of Baroque music.
Finally, there are several problematic notes on the traverso that one should be aware of whilst trying them out. Cross fingered notes like F, G♯, and B are typically quite muted—this is inevitable—but will speak better and sound more robust on different models (like the Palanca). It is typically hard work to get top F to speak, so even though they appear infrequently in Baroque music, it is something that should be considered. Finally, the instrument should ideally have its B, D, G, and A in tune in both octaves.