The influx of European and Eastern culture and technology to Virginia City during the 1860s was monumental and swift. See page xxi of the introduction to
By Ronald Michael James
In 1864 in America, William Sellers independently proposed another standard based upon a 60 degree thread form and various thread pitches for different diameters. This became adopted as the U.S. Standard and subsequently developed into the American Standard Coarse Series (NC) and the Fine Series (NF). The thread form had flat roots and crests that made the screw easier to make than the Whitworth standard that has rounded roots and crests.
Around the same time metric thread standards were being adopted in continental Europe with a number of different thread flank angles being adopted. For example the German Loewenherz had a thread flank angle of 53 degrees 8 minutes and the Swiss Thury thread an angle of 47.5 degrees. The standard international metric thread eventually evolved from German and French metric standards being based upon a 60 degree flank angle with flat crests and rounded roots.
Virginia City, briefly, was anything but typical. Ordinary banjo hardware would have been a long (long long) way from Virginia City. However, during the 1860s, the sophisticated mining machine shop would have been readily available. Again, I believe Tom Bree was working there as a machinist. And the wooden portion of the rim is almost identical to that made by his friend Charles Morrell in San Francisco for the Sam Pride banjo in 1863. There is no evidence of any alteration in the banjo anywhere. I appreciate the skepticism. I'm just telling you what it looks like from here. My impression is that the banjo was made between 1865 and 1870, Frisbee played it, his son Freddy played it. Then it sat. This area went from amazing connection to outside culture and technology to almost complete isolation by 1915. I'll look more at the hooks and nuts and get back to you.