Restoring the Williams 677 S, need a little help.

[strik9]

I was given this old Willliams wrench recently with a broken end.  I welded on a piece of steel to replace the part but now face a silly problem.
I don't know what size it was when it left the factory.

The long term goal is a nearly invisible repair and to restore the finish to as close to original as possible.  This one is too nice to be broken.

[Papaw]

Probably J.H. Williams 1/2" & 9/16" 677 Light Service Wrench S Style Wrench.
http://www.ebay.com/itm/J-H-Williams-677-Light-Service-Wrench-S-Style-Wrench-/280812271399?pt=LH_DefaultDomain_0&hash=item4161b73727