The standard Baroque oboe is generally made of boxwood and has three keys: a "great" key and two side keys (the side key is often doubled to facilitate use of either the right or left hand on the bottom holes). In order to produce higher pitches, the player has to "overblow", or increase the air stream to reach the next harmonic. The range for the Baroque oboe comfortably extends from C4 to D6. With the resurgence of interest in early music in the mid 20th century, a few makers began producing copies to specifications taken from surviving historical instruments.
Taken from https://en.wikipedia.org/wiki/Oboe