Observed Stokes profiles (dashed lines) and SPINOR 2D best-fits (solid red lines), in the wavelength interval 6300.90–6303.19 Å, at the location of the red markers shown in Fig. 1: panel a, from top to bottom: Stokes I/I_QS, Q/I_c, U/I_c and V/I_c in a pixel from the limb-side penumbra (red “*” in Fig. 1); vertical green lines in the blue wing of 6302.5 Å indicate the selected wavelength used to construct the Stokes Q/I_c, U/I_c, and V/I_c maps in Fig. 1 (−0.1 Å from 6302.5 Å line core). Vertical dashed lines were placed at 6301.5Å and at 6302.5Å, respectively. Panels b, c, and d: Stokes profiles in three pixels from the center-side penumbra (red “x”, red “+” and yellow “+” in Fig. 1, respectively) in the same format as in panel a. The SPINOR 2D best fits of profiles in panel d give B ~ 6.4, 8.0 and 8.3 kG, γ ~ 141,148 and 145°, and v_LOS ~ 5.6, 8.3 and 9.3 km s^-1 at log (τ) = −2.0, −0.8 and 0, respectively, with χ² = 14.