Nick intercepts one of Gatsby's business telephone calls. What does this call from Slagle reveal?

The call infers that Gatsby was pushing illegal bonds. We can not tell from Slagle's call whether they were stolen or counterfeit, so I'll just go with illegal.

“Young Parke’s in trouble,” he said rapidly. “They picked him up when he handed the bonds over the counter. They got a circular from New York giving ’em the numbers just five minutes before. What d’you know about that, hey? You never can tell in these hick towns ——”