rare as rocking horse manure, as, phr. — Green’s Dictionary of Slang

rare as rocking horse manure, as phr.

also rare as fairies, ...as a pregant nun, ...rocking horse shit, ...turds

(Aus.) a phr. used of anything extremely rare; also attrib.

1947		D. Davin For the Rest of Our Lives 112: I’ll never call them Rare as Fairies again.
1968		A. Buzo Norm and Ahmed (1973) 19: Course, you wouldn’t find that sort of thing around these days. Rare as a pregnant nun.
1989		R.G. Barrett Boys from Binjiwunyawunya 156: They’re as rare as rocking-horse shit [...] the first of their kind ever found here.
1993		Smith & Noble Neddy (1998) 229: Soldiers were a dime a dozen, but thinkers that had enough dash in them – as well as brains – were like finding rocking horse shit.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 331: This is the rare-as-rocking-horse-turds champion all-rounder.
2000		R.G. Barrett Leaving Bondi (2013) [ebook] ‘Tickets are rare as rocking-horse shit’.
2003		McGill Reed Dict. of N.Z. Sl. 169: rare/scarce as frog’s feathers/hen’s teeth/rocking-horse shit Extremely uncommon. ANZ.