Another test is to measure the distance from the top of the R in REG to the top of the T in VICTORIA. This is done with vernier callipers (for more reliable results take an average of 10 readings). Most of the proofs measure 33.6mm Other coins vary a good deal up to 34.6mm. This was a test introduced to me by Peter Davies of British Silver Coins. And no it is not a proof though the tone is rather pleasing on the obv.