During the 1956/57 season at the Ljubljana opera house Atilio Planinšek sang one performance of Manrico in Il Trovatore and one performance of Cavaradossi in Tosca.
During the 1957/58 season at the Ljubljana opera House, when Atilio Planinšek was already engaged as new dramatic tenor, he sang 9 performances of Manrico in Il Trovatore, 16 performances of Andrea Chenier, 8 performances of Erik in Der fliegende Holländer, 3 performances of Cavaradossi in Tosca and 2 performances of Radames in Aida.That is a total of 38 performances during the 1957/58 season.
During the next season 1958/59 at the Ljubljana Opera House, Atilio Planinšek sang 18 performances of Radames in Aida, 3 times Turiddu in Cavalleria Rusticana, 13 performances of Canio in Pagliacci and 5 performances of Manrico. Total: 39 performances.
Planinšek also sang during the 1959/60 season at the Ljubljana opera house, but as a guest: 2 times Turiddu in Cavalleria Rusticana and 2 times of Canio in Pagliacci, 5 performances of Manrico, 10 performances of Cavaradossi in Tosca and 3 times Andrea Chenier. Total: 22 performances.
I found also a Slovene translation of review of La Forza del destino with Planinšek in the Times of Malta, November 1959. It states that Licia Vallon (Donna Leonora) and Attilio Planinšek (Don Alvaro) showed beautiful voices capable of coping with any problem. The critic reports that they received a big applause after their arias. On the other hand, he thought their acting is not smooth enough. However this lack of acting smoothness was overcome by freshness of their voices. The critic praised also orchestra and choir under Maestro Cremagnani and excellent direction and staging by Cadro.
In the late 50's or in the beginning of 60's he was also Calaf in Turandot in Opera Hrvatskoga narodnog kazališta u Splitu (Croatian National Theatre in Split). As it is stated in the article, he was a favourite of Split audiences, a singer with one of the most beautiful voices ever heard in Croatia. (Source).
Planinšek was also Ismaele in two performances of Nabucco (29th July 1962 and 1st August 1962 as it stated in the article of Croatian Newspaper Slobodna Dalmacija, 22.7.2004. (Source).
Attilio Planinšek was also Radames on September 21, 1965 in Narodno pozorište (National Theatre in Belgrade).
In 1979 he was awarded a Milka Trnina (also spelled Ternina) prize (Nagrada Milke Trnine) together with soprano Blaženka Mili?.Nagrada Milke Trnine is awarded regularly from 1959 for exceptional artistical achievements in the field of music. (Source).