Andrew,
It's quite possible that there isn't an original stock. That Gemini stock was made about twenty years ago; around '98 Nibbs changed the grip to a true thumbhole, quite possibly after the UIT ditched 50m Standard rifle for Sport rifle. If the barrel is a 1913, it could well have been bought as a barrel/action specifically for that stock, not as a complete rifle. As Nibbs brought back select barrel/actions from Anschutz it may even have been bought as a package.
I quite agree about optimistic pricing, especially from dealers.
Edit: just looked at the updated photos, with two rearsights, foresight, and the gubbins, that would make a good deal.
VBull, if your mate is willing to sell the spare wooden but section separately, I would be interested.