Conn New Wonder "series I" Curved Soprano
Date: 1920. Image Courtesy www.VintageSax.com
All "New Wonder" Saxophones after 1917 had rolled-tone-holes. These days the community calls these the "New Wonder (series) I" or "New Wonder (series) II" saxophones. Conn themselves never referred to these as "New Wonder I" or "New Wonder II" but simply as "New Wonder".
In the following I am assuming that Conn's curved soprano's are basically of the same design as the straight soprano's. From what I have been able to infer from various sources on the internet, including this review by Thomas Zinnen of a New Wonder II straight soprano, the Conn 18M New Wonder I soprano saxophone was keyed up to F and had in-line palm keys. Additionally, there is a very strong possibility that a modern soprano saxophone mouthpiece won't work properly on this model, causing poor intonation. If you intend to play one of these, you will probably need to find a period mouthpiece. One avenue to explore would be a mouthpiece with a large chamber.