That means "Fender Special Run"..... thats the term they've been using on these short runs of special color MiM Strats and Tele's that you'll see if you browse a Musicians Friend catalog, or look on the website.
On the '06 MiM Standards, two of those former "FSR" colors are now full time color choices (chrome red, and electron blue) but they also made some MiM Tele's in Natural Ash. If only they'd make Ash a permanent finish option. Very Very sweet.