I never knew that RSI was Bob Reese and Bob Reese was eventually Springfield Armory?
https://www.thearmorylife.com/source-of-a-legacy-the-life-of-springfield-armorys-bob-reese/
I got two excellent Brazilian M98 7x57 barrels from RSI in the 80's. Never knew what/who he was.
Barrels marked FCSAP near the chamber end and a serial number of sorts at the muzzle end.
Got this from google machine
Paraphrasing what Dan said and adding some additinal info from Wikipedia: the abbreviation F. C. S. A. P. means
Fábrica de Canos e Sabres para Armas Portáteis (my Goggle translator says this means
"Factory of Barrels and Sabers for Portable Weapons"). F. C. S. A. P. was established near the city of
Itajubá, Brazil, on July 16, 1934 and it opened in 1935. It was declared the official place for weapons
refurbishment by the legislature on April 12, 1939. It was later renamed Fabrica de Itajubá (not sure exactly when),
which directly involved the Brazilian Army in the domestic production of military material, including a domestic
refurbishment of their older Model 1908 infantry rifles (Mod. 08/34.30) and their home-built Model 954 (Mq.30 M954).
In 1975 Fabrica de Itajubá was taken over and became a part of IMBEL (Indústria de Material Bélico do Brasil,
English translation is: Brazilian War Material Industry), which still makes war materials for the Brazilian armed forces.