Vintage hydrometer.
https://s3-us-west-1.amazonaws.com/h...r_fullsize.jpg
https://s3-us-west-1.amazonaws.com/h...1_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...433#post158454
https://www.homemadetools.net/forum/...168#post161153
https://www.homemadetools.net/forum/...722#post170752
