Deadfellas was originally designed to included 120 cards. In the process of negotiating the first print run, the card count was reduced to 110 for printing reasons. However, 120 was the "advertised" card count during the Kickstarter project, so the missing Mooks that were eliminated were printed as additional promo cards for loyal and generous backers (and pre-order customers).
The 10 Missing Mooks are:
Roberto "Rocky" Rizzoto
"Giggy" Franchese
Nicky "Nails" Nastassi
"Big Head" Mikey Altimari
Nicky "Glasses" Zicarelli
Johnny "Beach Ball" Baioni
Ralphie "Bubbles" Bendinelli
Angelo "Sockets" Milano
Bruno "The Rug" Pacelli
Petey "Popeye" Panzarino
These Mooks are added to the game and used just like any other Mook.