There were two groups of Brazilian 1917s. The ones shipped in the late '30s were built on the then current flattop N frame and would have had the large medallion service grips, as shown in GF's post.
Another shipment of Brazilians went out in 1946. These were built on WW I frames with the round top frame and could have the WW I style smooth grips.
Does your revolver have the flat or round top frame?