For valueing Geodex shares then 70% of $690M is a base. But remember this a pre-tax and pre-royalty value. A further deduction should be made to get the after-tax value for calculating Geodex share value. In the early years taxes will be low as capital costs and development costs are written off but will increase with time.
The only royalties will be government mineral royalties. My understanding of the Champlain agreement is that there is no royalty (NSR) due to them.
I'm estimating a $400M value for Sisson at the time of production decision ($4-5/share). As confidence in a positive mining decision is approached so will the $4-5 SP, over the next 2 years.
However, any increase in tonnage and grade, in the near future will increase the SP potential. I'd look to a $2 value by pre-feasibilty study release (scheduled for May 2008), then to $3-4 by feasibility study release (scheduled for Feb 2009) and top price by the time of debt financing and production decision (say early 2010).