Hi, I came across this and I'm missing this coin in my series.. anyway the seller is advertising this as a " ERROR COIN 1938 SILVER GEORGE VI TWO SHILLINGS COIN WITH PLANCHET ERROR, IMPURITY /GAS BUBBLE IN SMELTING ,INNER EDGE. PERFECT EXAMPLE OF THIS TYPE OF ERROR .MUCH SOUGHT AFTER ON THIS YEAR AND TYPE OF COIN."

ive never heard or seen this type of error on a coin.. do you guys think the coin was damaged after it was made or was it really an error as described by the seller?