A small typo perhaps ....... the Numista listing for this coin registers 1943 Australian Half Penny from the Bombay Mint Proof (as well as the 1942 year for the Bombay-minted half-pennies) as "1943 I," but the Bombay-minted non-proof half penny for 1943 is missing its "I" .......... It might help w/ coin identification to add the "I" to the 1943 left margin ......... ---all the best!
NOTE: There are a few Bombay-minted 1942 and 43 half-pennies (discernible by the dots before & after 'Half Penny" .... with no "I"s at all ....... but I believe these are rare errors
http://www.coincommunity.com/forum/uploaded/Sovereign%20Debt/20120421_1943-Iopt.jpg