Cjd, Australian and Victorian stamps bore me to tears. I haven't collected them for 50 years, so this is unfamiliar territory.
However, I see from Dave Elsmore's site
http://www.ozrevenues.com/Revenue-R...atalogue.htm that the first ½d stamp in the Victorian Numeral type (a surcharge at that) didn't appear until 1911. What did Victoria do for ½d Stamp Duty stamps from 1902 to 1911?