Postal rates became uniform between the new states on 1 May 1911 because of the extension of the United Kingdom domestic postal rate of 1d per half ounce (Imperial Penny Post) to Australia as a member of the British Empire. One penny became the uniform domestic postage rate. One penny postcards and lettercards also appeared in 1911. In the same year, the Postmaster-General's Department held a stamp design competition for a uniform series of Commonwealth postage stamps. This competition attracted over one thousand entries.