Could it be the same as the one from my '58 'VH' ??
The hole in the Banjo Union = 0.524 inches.
Banjo Union Head Diameter = 1.002 inches.
Copper Pipe diameter = 0.300 inches (or thereabouts - its a bit distorted after all this time).
Banjo Bolt Across the flats = 0.711 inches.
Banjo Bolt stem length = 0.857 inches.
Banjo bolt Thread Length = 0.527 inches
Banjo Bolt Thread Diameter = 0.512 inches (Remember its old).
Banjo bolt Thread TPI = 19 TPI. (= 1/4 BSP - 19 x 0.518" major diameter).
(Remember that BSP sizes are a bit odd - they are quoted a lot smaller than they appear !).
Probably not the same at all, but you never know
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH