1981 GL1100 front master cylinder rebuild

[MoreRacing]

Hi everyone
I'm in the process of rebuilding my 1981 GL1100. Doing the front master cylinder and I seem to be missing a washer that goes behind the circlip fastener on the rod that pushes the cylinder. Does anyone know the outside and inside diameters of this washer?. It's somewhat difficult to get a precise measurement
Thanks

[Rambozo]

Not super critical dimensions. The OD is just under the cylinder bore, and the ID is just over the piston center diameter.

[biguns]

The bore is 5/8th diameter.