This cleverly-designed object, designer unknown, was discovered by Arne the Kraftsman, proprietor of a vintage store in Australia known as the Kabinet. Arne explains what it is and how it works:
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“How can you resist such a great desk gadget? The item is a letter scale, to establish the postage amount. Marked with a 20 and 50 gram line. A halve circle aluminum bar, with a channel that holds a small steel ball.”
“The main surface of item is anodised black and the internal channel has a pink colour. I hope the last image explains how to use it. The age is 1980’s, my guess. I could not establish the maker or designer. I love stuff like this.”
Source: core77