The rear sight on the rifle is 3.75 inches ahead of the receiver. the sight elevates to the rear and has no side rails to speak of.  It is also adjustable for windage by rotating (loosening)a short lever at the fron of the assembly.
The rifle was purchased by my grandfather in the early 1920's as part of a government sell-off of surplus firearms following WW I.
Not sure what the "standard" rear sight looks like, but this one is very similar to those found on the 1903 springfield.
And yes, I hate the idea of altering the rifle, but have no intention of ever parting with it, I'll let the next generation of my family fight over it when I'm gone as I no longer have an heir.