If you want to find a matching retaining spring, here are the dimensions. The actual retaining spring will be one that meets the Military Standard (MS) which is also the part number.
Part# MS16626-1137
Retaining Ring
Notes:
Ring Material: Carbon Spring Steel (SAE 1060-1090).
Shear Strength of Ring Material (Ss): 150,000 psi.
Ring Specs
(D) Free Diameter:1.272 +0.010 / -0.015 in.
(t) Thickness:0.050 +0.002 / -0.002 in.
Groove Specs:
(B) Application Diameter:1.375 in.
(G) Groove Diameter:1.291 +0.004 / -0.004 in.
(W) Groove Width:0.056 +0.004 / -0.000 in.
Groove Depth:0.042 in.
Other Specs
(C) Clearance Diameter When Sprung On To Shaft: 1.730 in.
(C1) Clearance Diameter When Sprung Into Groove: 1.650 in.
(Pg) Theoretical Thrust Load Capacity - Groove Yield: 2,040 lbs.
Notes:
Yield Strength of Groove Material (Ys): 45,000 psi.
(Pr) Theoretical Thrust Load Capacity - Ring Shear: 5,399 lbs.