Hi Scott,
I thought that middle was an alignment shim, but I'm doing this from memory. The handle is what made me think that.
So the 1/16th may well be original then. It has the sharp 90 degree edges but just no 45 degree cut on the inside legs as the 1/8" shim which is why I though maybe I added it. Then again, I'm sure there were different suppliers back then too which may account for slight variances in shape.
Thanks,
Mike