CREATE TABLE table_31150 ("Name/ designation" TEXT, "Year of intro" FLOAT, "Country of origin" TEXT, "Primary cartridge" TEXT, "Major users" TEXT)

What country made the Flieger-Doppelpistole 1919?
SELECT "Country of origin" FROM table_31150 WHERE "Name/ designation" = 'Flieger-Doppelpistole 1919'
SELECT "Country of origin" FROM "table_31150" WHERE "Name/ designation" = 'Flieger-Doppelpistole 1919'