Sculpin, share certificates are an option, but not necessary. If your shares are held in a cash account, and NOT a margin account, I don't believe they can be used for shorting.
We talked about this topic in the past, and I know many of us changed our accounts to cash accounts from margin.
Legal and illegal shorting are both done in “margin accounts”. With a margin account the broker lends you a portion of the funds at the time of purchase and the shares act as collateral as compared to a “cash account” that requires that you pay for your stock when you make the purchase.
Also, your example of possible SLI value, to me is bang on, Minimum. You say 7 Million OZ between Tesoro & Vilcoro @ $100 per OZ in the ground, and you still come up with a SP North of $5 bucks. How much more conservative can those numbers get? That's also putting NO value on Cueva Blanca, or any of the BC properties.
Once they remove their very large block @ $2.50 (more than 350K shares), they don't have many to buy back, to cover, till you get up to the 73K for sale @ $38. Then who knows what comes after that? Guess it all depends on the News coming our way?
Very Glad I'm Long SLI, Not Short!