It was my understanding that Muskin does not produce any of their own RAM modules including "Mosel" REV2 DIMMs - they're simply a reseller that tests and certifies the ram modules as being PC133 CL2 (Cas 2-2-2) - which given the quality of these DIMMs is not too difficult to do. And since they now see a large number of people running (and reviewing) their REV2's at 150+MHz FSB, Mushkin is (now) certifying hand-picked DIMMs (again, picked from DIMMs they purchase/resell but do not make) as their "new" Muskin REV3 DIMMs that they guarantee to PC150 CL2.
edit - If Mushkin were actually making their own DIMM modules, then why do they only have the same modules as everyone else - that is, no 64MB nor 256MB Mosel REV2 modules? I'm sure that once they get a large enough "lot" of pre-tested Mosel REV2 DIMMs that they can guarantee at 160 FSB, they'll "release" the new and improved "128MB Mushkin High Perf REV4 PC160 222" SDRAM modules.