I tender you my sincerest apology for the obvious delay, my dear Mr. Carson, which occurred due to some unavoidable and absolutely uncontrollable official circumstances connected with my bureaucratic line of work. 
Although your esteemed friend from the WW2 Aircraft Net Forum, honorable Mr. Marcogrifo from Genova, was able to find some highly usable sources connected with that mysterious old birdie named C.N.A. Delta (for me it looks like a derivative of the good old Spartan Cruiser with different engines) I wish to call your attention to this tiny piece of information offered by my dearly beloved, specialized metadata crawlers, which are constantly connected with the Italian National Library service OPAC – SBN (Servizio Bibliotecario Nazionale):
Verdinelli, Armando
La Compagnia Nazionale aeronautica : 1920-1931 / Armando Verdinelli
Roma : Compagnia Naz. Aeronautica, 1931 (Roma : Grafia, S. A. I. Ind. Grafiche)
Monografia - Testo a stampa [IT\ICCU\CUB\0658946]
I think that in this book you will be able to find all those essential facts about that almost completely forgotten machine. 
Available examples are obtainable at:
Biblioteca Angelica - Roma (RM0290 ; RML06)
Biblioteca romana e emeroteca - Roma (RM 0275 ; RMRAC)
Biblioteca nazionale centrale - Firenze (FI 0098 ; CFICF)
And please accept our best thanks for the confidence with which you have hithertho honoured us.
BTW: It seems to me that nobody was interested for that almost completely forgotten Soviet mystery - Kocherigin TSh-3.
Well, perhaps our next offer from our unpretentious rarity cabinet will be a little bit more attractive deciphering assignment for all honorable participants of this distinguished forum.
In the menatime, as always - all the best! 