Raleigh Pioneer Classic

[Wookee]

Nah that wheel is a 27" whereas you have 700c, that big nut was a factory bodge, instead of fitting a thin cone nut they used normal nuts to increase the width of the hub* to fit a wider spaced rear triangle.

* they'd probably got thousands of those hubs to use up.

I'm going to take it into the LBS for them to have a look and try to get it lined up a bit better. As far as I can tell the rear triangle is the same width as my Classic and I might try swapping the wheels over to see what happens.

 

[SkipdiverJohn]

The nut used as a spacer is probably of no consequence, as mentioned already it could be a space filler because the wheel was designed for a narrower spaced stay.
However, if the wheel is off centre in the frame this needs correcting.
Given you have two Pioneers that ostensibly should be identically dimensioned, the obvious thing is swap the rear wheels between the bikes and see how they both fit in the "wrong" frame. It's quick to do, and most importantly, free!