The SF420FM is an S series solid body electric guitar sold by Ibanez in 1996. It was a spot model which never appeared in a catalog.
The SF designation meant that this model has a fixed bridge rather than a tremolo most S series models are equipped with. It was one of only a small handful of models offered in this sub-series.
Features of the SF420FM include a mahogany body with a flame maple top bolted to a 25½" scale Wizard II neck with a 22-fret rosewood fingerboard with dot position markers. Components include dual Ibanez humbucking pickups and a fixed bridge. The volume knob has a push/pull switch to coil tap the humbuckers.
The SF420 is a similar model without the decorative top. The SF470 is a somewhat similar model which has a third pickup which was available through 1994.
The SF420FM was discontinued after 1996. For 1997 a new series of hard-tail S models was introduced as the S Classic series. The SC420CM is somewhat similar.