Hello - I suspect Ivo is the person more qualified to answer this question, but in the meantime.....
I could be very wrong, but have a feeling that descriptions such as - 'opaline' and 'crystal glass' suggest very different types of glass, and I would have assumed that opaline did not contain any lead oxide (or at least not appreciable amounts) ............. although believe lead oxide is added to clear glass, usually, to improve the refractive properties and make it easier to cut. Full lead crystal usually contains something in the region of 34% lead oxide - although lesser proportions are quite common I believe.
It's always possible that your jade coloured box has the wrong sticker - this can happen. As an opinion only, your box looks possibly to be an item from a woman's trinket (dressing table) set.
If you hold the box up to a strong light, does the transmitted light show a slight orange or sunset glow - this is usually one of the properties of opaline glass.
Very nice box by the way

Very much regret we don't provide values on the GMB - the value of any piece of glass is a very personal matter, and with the quantity of members I suspect you would end up with many different values, which would be confusing - sorry if that sounds a bit negative - your best source of values would be auction catalogues, both on line and paper examples by visiting auction houses.
