Dick,  Isn't it unusual that the stock would be replaced with such a late model, but the handguard, band and sight would still be from the original period?  Would there have been some special provision  in the change to allow for the shorter length of the guard and therefore the band position?  Maybe this was all done by a later owner who was trying to preserve as much of the original carbine as he could.  It looks like there might be a seam under the band.