Repair Carl weak spring Rostfrei (slant) 23cm Italian Transitional Stiletto vintage automatic knife

Vintage 23cm Italian Rostfrei diagonal stamp swivel bolster stiletto switchblade knife made in the 1960s or 70s in Italy. The knife measures 22.5cm (8 7/8 inches) open with D stamped brass liners and nickel silver bolsters, button and safety cap. The flat grind swedge blade is 98% full or better with original factory finish and a few light scratches and is marked Rostfrei in script diagonally (slant) on the ricasso. Tiny bit of the tip missing and not great sharpening. The genuine horn scales (handles) are in good condition with one tiny bug bite by the button and mostly black with some tan & cream streaking. The knife works well with the blade tip deep even with the liners closed