I was going through the uCurrent project and noticed something that seemed unusual to me. In the image, the trace connecting R1 to the input jack is (a) of differing trace widths, and (b) has no solder mask for a small portion.
Does anyone know if there's a reason for a small portion of the trace to be different from the rest? I can't think of an electrical reason, except maybe controlling the trace impedance with a different trace width but that doesn't explain why there's no solder mask. Is the exposed trace meant to help during testing?