Background-subtracted, vignetting-corrected, and mosaicked count-rate images of Calvera’s SNR in the 0.3–1 keV (left) and 1–2.5 keV (right) energy bands. The area used for the spectral analysis of the brightest diffuse emission (divided into north, central, and south regions) is identified with the white polygon. The white ellipse marks the clump region and the white dashed ellipses are the two regions used for the background. Calvera pulsar is shown with a yellow dashed circle. Fermi/LAT contours from Fig. 1 are overlaid in gray. The green box marks the TNG/DOLORES area of pointing P4 in which the smudge is detected (see Fig. 8).