I was recently able to purchase this Gibbs Farquharson.
It is a late top tang safety model from 1910 which was rebarreled to 256 Dutch Mannlicher in 1920.
It also has what remains of the special sight which is designed to retract into the comb of the stock. This feature was previously thought to only be on #973 and #974, the last two Gibbs Farquharsons made. This is #971.
As of now, I have the pleasure of waiting for my background check to complete. So in about a week, I will be able to take it home.