Misc: In 1971 Supreme Court overturns ---------- conviction of Muhammad Ali.?

Questions

The birthstone for which month is opal?

Which russian jeweller exhibited his mperial Easter Eggs at a Paris Exhibition of 1900?

On a hallmark, which metal is indicated by a Lion passant in England and a lion rampant in Scotland?

Which King introduced the statute which instituted hall marking in England?

What is the name given to a gem made from 2 stones arranged in differently coloured layers, with figures carved into the top layer, which is set in relief against the others?