12 gauge is rather thick , (But I cant measure your stuff from here)
more likely bike industry typical 14 gauge, 2 mm thick (15 is 1.8 mm)

AWG also applies to copper wire in electricity,... spokes are mostly stainless steel wire.

12 (American Wire Gauge) is 0.0808 inches (2.053 mm)
I see thick spokes used on Brompton's rear wheel spokes measure roughly 2,2mm..

Nips are usually brass, they often break when spoke is too short, So does not come up to the end of the nip.