Side cover knob external retaining ring
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
The original side cover screws have a groove to accept and
E clip style external retaining ring (MG# 90280005). The groove for this ring is 4 mm in diameter and ~0.9 mm wide. McMaster-Carr part number 98543A112 (black phosphate spring steel) or part number 98317A214 (Type 420 stainless steel) fit well.