Green’s Dictionary of Slang

1. a small-time confidence trickster.

1925		E. Jervis 25 Years in Six Prisons 17: ‘Tweedling’ [...] is this: You buy a real, genuine eighteen-carat-gold watch-chain for about twelve pounds; and also a few of those made in Birmingham [...] The chain is handed over in the tissue-paper, and the ‘tweedler’ departs. But it was the Brummagen chain that the ‘can’ got.
1938		F.D. Sharpe Sharpe of the Flying Squad 275: One of the oldest methods of crime is the Tweedle. [...] The Tweedler spots a ring worth a lot of money in a jeweller’s shop and goes to great pains to have an exact though worthless replica made. He goes in, asks to see the tray containing the ring, and when the assistant isn’t looking very carefully susbstitutes the fake for the real thing.
1941		V. Davis Phenomena in Crime 79: The ‘Tweedler’, the possessor of a dud ring or imitation gold watch who tries his swindle [...] on any unfortunate.
1959		J. Gosling Ghost Squad 114: The terms ‘conning’ and ‘tweedling’ cover virtually everything from the sleight of hand of the three-card trickster to the glossy prospectuses offered by the promoters of bucket-shop concerns [ibid.] 118: The tweedlers’ defence is that the ring produced in evidence is not the ring they sold.

2. a stolen vehicle which is passed off as perfectly legitimate.

1977

D. Powis Signs of Crime 206: Tweedler A stolen vehicle disguised for ‘honest’ sale to a respectable dupe.