Per le carrozze uso il sistema officiale UIC (Union Internationale des Chemins de fer). Ecco un esempio.
I use the official UIC
(International Union of Railways) coach code system for my coaches. Below an example. 

©  Mats Verschuren, 2011
Everything available on this website is available for free. All objects, trains and other content available on this website are made by Mats Verschuren. All this content is copyright Mats Verschuren. Changing or spreading this content, someway, is strictly forbidden without the permission of Mats Verschuren. You automatically accept everything written above if you download something from this website.