Congress to Define a "Dollar?"

??? This was already done through US Weights and Measures and the Coinage Act of 1792.

The Act established or defined the "dollar" as a weight of silver (371.25 grains (troy) of fine silver) and then regulated the value of gold coins to it in a 15 to1 ratio, that is, as 15 grains of silver to every grain of gold. The regulation also included establishing the purity and the various denominations.

Bill: https://www.congress.gov/bill/115th-congress/house-bill/5404?q=%257B%2522search%2522%253A%255B%2522H.R.+5404%2522%255D%257D&r=1

Coinage Act of 1792: http://www.logoplex.com/shops/leaders/coinage1792.txt