Just picked up this Cabela's 3x Tactical Prism sight, which was sold because the reticle no longer illuminates. Tried new battery - obvious. No joy. The only manual on the web doesn't show much info. Any thoughts on possible repair? I'm happy to use the non-illuminated reticle only, but if it's an easy fix, why not? Any idea what is behind the small circular port with the two-dimples for a removal tool? Image shamelessly stolen off the web....