Panerai. A very rare and massive stainless steel wrist depth gauge with diver’s knife

Panerai. A very rare and massive stainless steel wrist depth gauge with diver’s knife
Signed Luminor, Panerai, Metri, circa 1940
Black matte dial, outer dot and Arabic 2.5 meters luminous divisions, inner baton five meters luminous divisions, central transparent luminous hand, massive stainless steel case, back secured by six screws, inner double ring secured by six screws locking case and case back together, Perspex dome, stainless steel buckle, case and dial signed
69.5 mm. width, 90.5 mm length, 39.5 mm. heigth