Definition of "jargoon"

[…] he would sigh and gently lay it aside with a slow shake of his head and the slightest raise of an eyebrow. He said that sometimes even “jargoons” or fake jewellery could be worthy of respect, […]

2011, Tony Broadbent, The Smoke

By the time the buyer had discovered his mistake, there was nothing he could do about it. Similarly with the 'jargoons', except that here the jewellery sold was fake from the start and the seller had to rely on faster talking and a quicker sale. […] Reggie had a way with him. People trusted him, and he could always pick up a few pounds when he needed them from the jargoons and the tweedle.

2013, John Pearson, The Profession of Violence: The Rise and Fall of the Kray Twins