The arrow in this photograph shows the distance between the line of the bridge pins and the inside of the bentside. This distance is uniform along the entire length of the bridge and is measured to be very close to 6 once = 129.7mm.
This instrument, which has been attributed by me to Onofrio Guarracino, belongs to Signora Fernanda Giulini, Villa Medici-Giulini, Briosco, Italy.