You won't be able to easily replicate the Beretta finish, as it is likely not a good idea to put any sort of PVD coating over the current nickel plating. My best guess would be that it's TiAlN, or at least that that'd be as close in a commercial coating as you'd get. To do it right you'd need to strip the existing finish, prep the metal, and have it plated, all by someone with a FFL. If you could get it done properly (sorry, cerakote is not a proper finish for a DT11 in my opinion) I'll bet you'd be somewhere around $1k by the time you're done if you want something that is indistinguishable from the Black finish.