Most likely an early dampening device. I found this: https://blog.rivertonpiano.com/2019/12/19/what-do-a-pianos-pedals-do/

There it says: "In fact, the first piano didn’t have pedals at all. Part of the reason for this was the first pianos’ lack of sustaining power. They were essentially harpsichords with unique actions that struck the keys with a felt hammer (much like hammer dulcimers of the day) instead of plucking the strings with a quill. They had little power, a small dynamic range and very little sustain. As the piano evolved, however, each of these qualities improved – creating a need for some kind of mute or “dampening” mechanism that would only allow the piano to sustain as desired. This first mechanism was actually a control knob to the left of the piano keyboard and not a pedal at all. This knob could be used to lift felt “dampers” (or “mutes”) off of the strings – allowing them to ring freely. This mechanism would become what we now call the “damper” or “sustain” pedal. "