I think that even though the older brittania's were less pure they still had 1 ounce of silver just the coins weighed slightly more i may be wrong but i read it somewhere , i think i bought an early one and thats what the info said id have to check though :)
Yes i thought so it was a 2011 i bought
Weight (grams): 32.454
Pure silver content (grams): 31.10348
Fineness: 958.4
Dimensions: 40mm diameter X 3.1mm thick
As usual, this British Silver Britannia contains one ounce of fine Silver, but the coin itself is heavier as it contains 95.8% Silver.