Hola, kurios. Welcome to the Forum. Que' fue? The airweight 'blue' gun does not have a blued finish frame like the steel models, but an anodized 'aluminum black'. I don't know how far your finish is gone; 'blued' 37 models normally show finish wear/thinning on the frame edges and corners.

Birchwood Casey used to offer an 'aluminum black' touch-up solution in a 4oz bottle, don't know if that will suit your needs. The cylinder, crane, barrel are steel and regular bluing will work on them.

Hope this helps. Co'lo suave!

Kaaskop49