A search of the National Archives catalogued Medal Index Cards at
http://www.nationalarchives.gov.uk/records/medal-index-cards... revealed several Capaldi soldiers, but only one Joseph.
Description: Medal card of Capaldi, Joseph
Corps: Royal Engineers; Regiment No: 282850; Rank: Sapper
Corps: Royal Scots Fusiliers; Regiment No: 47518; Rank: Sapper (sic)
Corps: Royal Engineers; Regiment No: WR290400; Rank: Sapper
Ref WO 372/4/10380
High quality colour scans of the original MIC’s are on Ancestry an I would advise getting a copy of that rather than the poor quality b&w scans from the NA that are from microfilm.
Check the WWI Medal Rolls, also on Ancestry and his entry may give dates he served with the Royal Scots Fusiliers.
You should also check if a service or pension file exists for him. Also on Ancestry, but as there was no need to provide a birth certificate to enlist, any file is very unlikely to contain a birth certificate but may have more complete details.
This may help you obtain a copy of the birth certificate
https://familysearch.org/learn/wiki/en/Italy_Civil_Registrat...