The M1912 was sold to Chile, Colombia, and Mexico (some were kept by Austria for WWI and designated M14). The siderail was marked Modelo 1912 on the Colombian rifles but marked Waffenfabrik Steyr on the Chilean and Mexican rifles. It looks like your rifle was either Colombian or Colombian kept by Austria - not Brazilian (the M1912 was not sold to Brazil). If kept by Austria, it should have an extra large rear swivel loop to fit the Austrian sling. That is to clear the buckle sewn onto the front of the Austrian sling.
Originally it would have had only a rear sling base with no loop, made for a detachable swivel.
M14 rear swivel
Austrian sling on front swivel
Austrian sling on rear swivel
Rear sling base with no loop on a Chilean M1912 rifle. The detachable swivel is attached to the trigger guard in the photo, to put the sling in the parade position.