In full disclosure, I've never had a M70 DBM in the shop so it's very possible that "E" designation in your rifle is for that specific bottom metal..
However, the .300WM, .7mmRM etc in the Classic M70 uses an "ML" box... The PF actions use a "BR" magazine for those rounds.. This comes right out of the Winchester parts book..
The "E" box is obsolete, but was used for the 7mmSTW & .300 WBY magnum in M70s with S/N below G318388... It's not shown as an option in the PF parts section.
