"He never said it was stolen from Lombardi. In fact, he implied that the contact he was intending to meet was to be Jack Lombardi, which I derive from the statement that "Wait, you aren't Jack Lombardi." and the sudden gunfire. We know the mark was intercepted and that there were atleast 3 parties involved:
1) Friedrich and his men - the sellers.
2) Jack Lombardi and his men, presumably the dead men in the alley. The intended buyers (who Friedrich was very startled not to meet).
3) "Black" and his men - the interceptor.
Also, from the conversation, we know that the contact, this Lombardi, represented a Mafia family because Friedrich inquired why a Mafia family wanted to purchase the case. Hence my assumption that he is probably American. Or even a New Yorker.
Black must be an agent of the original owner, who wanted his merchandise back. Since he is traveling back to Japan, I sincerely doubt he represents the Mafia family."