Tool box knob external retaining ring
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
The original tool box screws have a groove to accept an
E clip style external retaining ring (MG# 12478600 or MG# 55478600). The groove for this ring is ~8.3 mm to ~8.4 mm in diameter and ~1.15 mm wide. McMaster-Carr part number 98543A116 (black phosphate spring steel) or part number 98317A227 (Type 420 stainless steel) fit well.