#3 Thought of another application for this symbol and was wondering if there are more? The one I recalled is its use as a symbol for "mesh" - as used in laboratories to describe the aperture size of a screen (sieve)

My wife, who works in the medical field, was taught to use the # as an abbreviation for "pounds," when noting weight measurements. It is commonly referred to as the "pound sign" here in the US, but I wonder if the name came from the practice of using it as the abbreviation, or if it was used for the abbreviation because of the name.