Nucky says he needs a partner with $500k to invest into his new Florida venture. That night Rothstein loses close to that amount to him on gambling table. Now Nucky has the money he needs but he's still looking for a venture partner. It makes no sense since he got the money he needed when he won on the table.
When Dean O'Banion fires the double-barreled shotgun, the sound effect implies an automatic weapon, complete with ejected shell casings.
Narcisse mentions Marcus Garvey's deportation in this episode set in 1924. Garvey wasn't deported to his native Jamaica until 1927.
When the Capone Brothers drop off George Mueller/ Nelson van Alden to his partially built ''pre-cut house'' there is building rubble, saw-horses and a toolbox visible on the sidewalk outside the house. No tradesman or even an amateur would leave a toolbox outside and susceptible to being stolen.
Early in the episode O'Banion is shooting a double-barreled, side-by-side shotgun which must be re-loaded by opening the breach to remove the spent casings. Immediately after he fires it, the sound of a pump-action shotgun (which is reloaded by "racking" the slide beneath the single barrel in order to eject the spent shell casing and insert the fresh round) is heard.
This mistake is repeated before the end of the scene as O'Banion threatens Nelson Van Alden.
Dean O'Banion is using flowerpots for target practice with his double-barreled shotgun. The sound of a slide actuation on a pump shotgun is heard, when no slide is present on O'Banion's shotgun.
Mr Rothstein is reluctant to invest $500k in a new venture with Nucky because he is supposedly risk averse and doesn't want to lose money, yet he loses close to that amount in the gambling table in one night without a problem. If he's so risk aversive that he is reluctant about investing $500k into Nucky's Florida business, he also wouldn't be gambling close to that amount playing cards.