I would just start with the last time GCY was valued by an...

I would just start with the last time GCY was valued by an actual bidder i.e. WGX before all the dilution since.
Look at what it had of value then and deduct what you consider that immediate value to a buyer was worth to them back then that NO LONGER EXISTS.
Then ADD to that the costs of getting it to that same state again and the value of that time cost and RISK wise .

I.e. Immediate profit income from the day ONE of a takeover with an operating mill running at about break even with around 1yrs worth of ore ahead of it.
Could be immediately made more profitable with trucking of higher grade stockpiles.
Compared to recommisioning costs etc,having to stockpile ore ,get staff,fix problems arising from care and maintenance and so on.and paying out a lot of cash upfront before ANY cash return comes in.
Add in the extra royalty costs.

What would you pay for a car sitting in a paddock with grass growing around it the same year model colour as your one that hasn't run for a year or three?
What's the cost of getting that running and back on the road?
Are you in the market for such a great deal?
Scrap value less liabilities such as taking it to a scrap merchant,mechanic,or is it a rebuild project over time?
I'd prefer to go less complicated and leave it well alone.

In the end your guess is as good as mine

DYOR + DYODD