The 1854-59 printings were all imperf.
1860-72 printings were perf 12 or 13. Later printings were perf 10, 11, 12 or 13 or just about any combination of these

Gibbons lists two types of Crown over NSW watermark - from the 1872-1902 printings and the 1882-97 printings. Taking your stamp as blue-green/bluish-green and perf 10, it would be SG 215 (£22) first watermark or SG 233 (£1.75) second watermark. Someone who knows these stamps might be able to tell from the lettering which you have, but NSW aren't my cup of tea (despite having been born there

)
(Looking at your scan again, I'm pretty sure that the crown is the second type, so your stamp would be SG 233.)
Incidentally, Gibbons mentions your South Australian REPRINT in a footnote, but doesn't give it a number or value it.