Titleist 735 CM "FSS" irons

Hey all,

I just picked up a beautiful used set of Titleist 735 CM irons stamped with a hammer and anvil and "FSS."  I used to play the chrome version of these irons and I know there was a stainless steel version made, too.

BUT - does anyone know what "FSS" stands for?  I can't find anything much online.

Also, the set is 4-PW.  All the clubs have the stamp except the 7-iron and PW.  Any thoughts as to why they don't have the stamp?  Replacement clubs maybe?

 

Thanks!

 

OK...I'm thinking FSS stands for Forged Stainless Steel.  Some on on GolfWRX said the ones with the anvil stamps are prototypes.  Can someone from Titleist confirm?