The 1 shilling is very rare as it was the last stamp in the series, issued about April 1880. The proofs for the other stamps in the series were produced in 1879, before this stamp was needed and that is why they are so rare for this issue.
According to Ken Scudder, there were two groups of proofs, and I have only seen singles, no pairs or blocks:
- Mauve imperforate colour proofs watermarked Crown over Q type 2 paper approved around April 1880
- Deep reddish violet Imperforate colour proofs watermarked Crown over Q type 2 paper from around April 1881
Imperforate singles in several shades are also known and these are probably proofs as well.
1 shilling imperforate mauve plate proof on watermarked Crown Q type 2 paper. Ex Alan Griffith
1/- deep violet with parts of 3 adjoining units but touched at the right, unused. Ex Manning
1 shilling imperforate plate proof. Seen in Corinphila auctions 2018
1 shilling mauve proof. Courtesy of Dave Elsmore, Queensland stamp collecting Facebook group. Indistinct date