The markings are somewhat confusing to me too. As far as I know, the Buck Striders do not have the Buck model number on the blade nor "USA" unless it is part of the BOS logo. For instance the 889's with run of the mill 420HC don't have USA anywhere on them. I'm not sure about the 420HC 890 fixed blades because they are supposed to be BOS treated.
So SB obviously stands for "Strider/Buck" and SBMF is the Strider model designation for the design (SMF) with the "B" added for Buck. According to Striders web site: "The names of our models come from several things, some are the initials of the person the knife was designed for, sometimes the name has a personal or funny meaning to us, and sometimes the initials are those of a warrior or hero we wish to show our respect."
Below I've updated the original 2002 post from Joe H.
http://www.bladeforums.com/forums/showpost.php?p=1832983&postcount=9
SB1 = Strider Buck (880) larger folder in either tanto or spear point
SB2 = Strider Buck (881) small folder in either tanto or spear point
SB3 = Strider Buck (890) fixed blade in spear point (and tanto?)
SB4 = Strider Buck (889) SBMF folder in Black, OD Green, or Coyote Brown
Is the 882 also marked with SB4? And where does the 888 Solution fit into all this? It would be nice to have some sort of time line or cheat sheet for all the Buck Striders like PR mentioned.