Mossberg 500 20ga bolt design - "rocker"?

[AreWeNotMen?]

So I was going through my daughters Mossberg 500 20ga (youth/Bantam model?) and in reading up on bolt disassembly, I find her's has what's referred to as "the old rocker design"...which does not use a firing pin spring. I bought it in 2007 or so. Given that our 500 is not "old" - could it be that all 20ga 500's have this design? Anyone have insight on the evolution/types of bolts used in the 500's?

Thanks.