Hi Jerry, thanks for getting in touch. The YOB-431B has a Simplified Conservatoire system (semi-automatic octave system) with a thumb plate. But we'd recommend also looking at the YOB-431MBE Mk II Oboe - link below.
The YOB-431MBE Mk II also has the semi-acoustic octave system and thumbplate but, unlike the YOB-431B, has our Duet body. A Duet body is made from a combination of grenadilla tonewood for the outer body and - in the case of this model - a precisely-shaped ABS resin inner body. This offers substantial benefits to oboists over conventional oboes, including improved tonal consistency and durability.