You will look forever with no positive result, The 39 convertible windshield gasket does not have a seal groove for the stainless ring. I think you are confusing this with the 1941-48 style gasket that has a stainless ring applied to the seal rubber. The stainless steel trim is a separate ring on a 37-40 and captures the pinch weld of the window opening sheet metal. The gasket to seal the glass is applied around the glass and installed from the rear and held in place with the windshield garnish molding.