I think Penumbra Sans Light is still correct. The sample may have deteriorated the stroke width, or this may be an instance of the older Multiple Master version of the font.

I second what Stephen says. If you overlay Penumbra on your image the character shapes are almost a perfect match. Obviously the kerning needs to be matched and the quality of your scan makes the actual weight of the font difficult to work out. But this is definitely Penumbra Sans.