Only marking on this item is Japan and that would confirm that this piece is a post-WWII pocket loupe magnifier.  Likely produced through unbranded novelty channels in the 1950s and 1960s.  Designed for hikers, scout groups, and map readers.  Small oval tin or chrome-plated casing??  houses a loop that swing out to allow the user to easily read dense topographical map markings or fine text.  The metal has some marks, corrosion and scratches...all very minor....I did not try to clean.