The worst that can happen is that you open it and find that it's flat or, alternatively, it's so damned fizzy that it all ends up on the ceiling. Otherwise it should be fine to drink. Give it a go!
^^^ You need to divide 'proof' figures by two to get % ABV, Prudie, but even then the figure seems to be rather high, as Champagne is typically around 12.5% to 13.5% ABV.
I suspect that it's actually a half bottle, containing 37.5cl.
I'd love a bottle of champagne, I celebrated a good old birthday during the year and the one thing I missed was a bottle of bubbly - I'm going to buy a bottle for the new year