Green’s Dictionary of Slang

a coin or money, usu. a halfpenny.

1834		‘A Grand Turn-Up’ in Randy Songster in Spedding & Watt (eds) I 187: He used to sweep the crossings [...] and cadged a tidy lot o’ posh too.
1838		Crim.-Con. Gaz. 1 Sept. 24/3: Mr Vanderspooney, in reality no spooney [...] now had enough posh to open a crib in town [...] as a Surgeon Dentist.
1839		H. Brandon Dict. of the Flash or Cant Lang. 168: The paper makers get the tats and never tip the motts a posh.
1840		Flash Mirror 12: ‘Oh! These are wicked times! [...] The nobs vill keep all the posh to themsleves, while a poor honest creeter can’t even make an industrious livelihood’.
1857		‘Leary Man’ in ‘Ducange Anglicus’ Vulgar Tongue (1857) 41: But let this be your plan: / Put up with no kiboshery / But look well after poshery.
1862		J.A. Hardwick ‘Rob the Rhymer’ in Prince of Wales’ Own Song Book 69: Your master looked so well and sleek [...] When he had lots of poshery.
1870		Hotten Sl. Dict. 204: POSH, a halfpenny, or trifling coin. Also a generic term for money.
1882		Sydney Sl. Dict. 10/1: Where’s all the talent, Betsy? Where’s our jokers? I haven’t had a drop of lush since they went out with Tiger Liz, and I must have some white satin, though I haven’t a posh about me. Tip us a peg. Where’s all the company, Betsy ? Where are our fancy men? I haven’t had a drop of drink since they went out with Tiger Liz, and I must have some gin, though I haven’t a piece of money about me. Give me a shilling.
1882		Dly Dispatch (Richmond, VA) 1 Nov. 3/3: A ‘posh’ is a small piece of coin.
1893		P.H. Emerson Signor Lippo 106: Years after Bottle Nose died, leaving his posh to Blower.
1895		C. Crowe Aus. Sl. Dict. 60: Posh, the term for a small coin, a halfpenny.
1899		A. Binstead Houndsditch Day by Day 94: He could shpend de poshers a goot deal faster dan de olt man could make ’em.
1906		E. Pugh Spoilers 78: Pay or toss, as you like [...] Tain’t a question o’ posh wi’ me. I got a brightful.
1912		E. Pugh City Of The World 274: He must be fly enough to pipe off a man at a glance, to tell whether he’s got a brightful of posh or only his kip-money in his sky.
1922		Dundee Eve. Teleg. 19 July 2/4: [A] halfpenny is a ‘brown’ or a ‘madzer (pronounced ‘medzer’), ‘saltee’ [...] ‘mag,’ ‘posh,’ ‘bawbee,’ or ‘rap’.
2011		J.J. Connolly Viva La Madness 54: What was all that performance in the bank [...] Why’s he bringing his poshes halfway round the world?