The Special Correspondent sent me the following link to the website of the Duke of Castro and his branch of the House of Bourbon Two Sicilies - as opposed to that of the Duke of Calabria - and added that there are some rather good interactive stuff if you click on the shield on the website. The site itself is http://www.realcasadiborbone.it/en/history-documents/royal-symbols/royal-house-coat-of-arms/
For some background on the history of the monarchy see the online article Kingdom of the Two Sicilies, and on and more specifically on the disputed succession since 1900 look at the section
I have added the website to to the sidebar as House of Bourbon Two Sicilies - Castro line.
The Royal Arms of the Kingdom of the Two Sicilies
Image: Wilkimedia Commons