The Coronini Cronberg Historical Archive comprise about a thousand folders containing documents dating from 1257 to 1990. The extensive reorganisation work carried out after Count Guglielmo's death led to this material being divided into four major sections, identified according to content and chronology.
- The Current Administration brings together manuscripts, typescripts and printed matter mainly concerning the administration of the family estate, dating back no more than 40 years.
- The Study Materials contain documents dated between 1952 and 1990 that are closely related to the figure of Guglielmo Coronini and his activities. This therefore includes printed matter, typescripts, photostatic reproductions from documents and editions, invitations to cultural events, notes and letters concerning his studies of a historical-artistic nature, such as the great historical work Gorizia comitale, the collaboration on the exhibitions on the 18th century Gorizia (1956), on Giuseppe Tominz (1966), and on Maria Theresa and the 18th-century Gorizia (1982), as well as papers pertaining to his activities within the regional Heraldic-Genealogical Commission and the Sovereign Military Order of Malta and documents of the local section of the Italia Nostra Association, of which he was president, in addition to notes, sketches and drawings.
- The Acts and Documents comprise all the documents, letters, account books, notarial deeds, that make up the actual Coronini Cronberg historical archive, but also include the archives inherited from other families, such as the Rabatta, Cobenzl and Cassini archives, or acquired due to Guglielmo's collecting interests, such as the pieces of the archives that belonged to the Attems-Petzenstein and De Grazia families, or the collections assembled by other scholars and erudites, such as Gaetano Perusini and Ranieri Mario Cossàr. This section is therefore home to documents dating between 1257 and 1970, including the valuable collection of parchments, directly related to the Gorizia Comitale project, the great historical work dedicated to the Middle Ages in Gorizia, which remained unfinished and on which Count Guglielmo worked throughout his life.
These three sections of the Coronini Cronberg Historical Archive are currently deposited at the State Archives in Gorizia, located at Via dell'Ospitale 2, where they are accessible for consultation.
- The last section is that of the Photographic Archive, which contains photographs, negatives, plates and slides, up to a total of 12,000 units, dating back to the 19th and 20th centuries, partly related to the family history and partly commissioned by Guglielmo himself for study purposes. The photographic archive, still awaiting reorganisation and cataloguing, is kept at the Coronini Foundation headquarters.
