Story from Jaume (Andorra)
The CNIA (Centre Nacional d'Informātica d'Andorra) and CASS (Caixa Andorrana de Seguretat Social)
The CNIA was created at September 26th of 1978 by decree of Consell General de les Valls d'Andorra with the objective of providing computerized services and solutions to the country's administration. The organization first deployed at least one S3/12 from 1975 to 1979 when it was replaced by an unknown number of S3/15, one of them being the unit listed in your site. The system operated alone until 1982, when a S/38 was introduced and replaced it as (one of or) main computers of the corps, the information about the number of units is not clear, but knowing the cost should have been very high and my country is what it is I think they had only used a single model 12 and a single 15.
After being displaced, our unit eventually became the central computer of CASS until it was eventually phased out in 1988. Note that, from November 7-9th of 1982 there were the infamous floods that left many personal and massive material losses; as CNIA's HQ were located at the current CASS building, main floor. According to Aleix i Camp, the main computer room was flooded quoting him textually "leaving there more than a meter high of mud and rubble". According to him all programs were lost but backups were already left at two bank safes, one nearby (I think he is talking of an office from Crčdit Andorrā) and another in Escaldes-Engordany. The first set of backups was destroyed during the disaster, but the second was retrieved safely and according to him service was restored thanks to "other businesses which had similar computers" (implying other S/3, S/32, S/34, S/36 or S/38 were operating in the country). Now I see a statement in the book which talks about "substitution computers", I don't know if this implies replacement modules to repair the computer or full swap (if it's the later, then sadly the foretold story is a nice background but would not be our unit). The computer would have been operating under CNIA control for CASS until 1978, when more powerful midranges like the AS/400, S/36 5363 and other smaller but more powerful midranges became available.
CASS/CNIA's early Headquarters: https://goo.gl/maps/ZwryGKikVY6EBpy19
Consell General (Casa de la Vall): https://goo.gl/maps/YzF2QEehvy2suto56
Main Government building: https://goo.gl/maps/nsBXCttamKaFJ4338
Credit Andorrā's office where I suspect the first backup set was located at the time of the floods: https://goo.gl/maps/3s29UJX69Dx72xJU6
The second backup set was located at the time of the floods: https://goo.gl/maps/P6LmWaDXQcCZUXJx8
Reference: "Inicis de l'Administraciķ andorrana moderna, 1961-1978", ISBN: 978-99920-61-61-9), in which there is an article by one of the implicated engineers ("El Centre Nacional d'Informātica d'Andorra i la transformaciķ digital de l'administraciķ" by Jordi Aleix i Camp).
Decline: Escola d'Informātica del CNIA i Universitat d'AndorraIn 1988, CNIA made a plan to overhaul the hardware. It was implemented over the year and consisted in the replacement of the older S/38s and System/3 by the then-new AS/400, S/36 compact and other S/38s. IBM PS/2 were also introduced to control certain small but strategically important parts. Therefore the System/3 was now completely outclassed and out of the administration main roles. Still, they found an utility for it: as far as I know S/3 programs should run on S/36 systems and they used that compatibility to use it as a didactical computer. They founded a state-run school to teach programming on microcomputers using PCs (IBM 5150 and 5160) and new PS/2-30/50s and the System/3 to train on business systems. Eventually, the aforesaid school merged with the infirmary school and that event led to the foundation of Andorra's first university.
The computer continued to serve in that role for an unspecified amount of time until it was retired. The unit was placed in one of the main building's corridors. After that peripherals were lost and the cpu unit fell in disrepair, with students vandalizing it. It remained there for a large number of years until the organization decided to remove it, found a museum in Cáceres and sent it.