Savage magazine differences

[Enfield trader]

I have just noticed recently that I have 3 Savage magazines all a little different.

Solid base with pips
Solid base without pips
Split bottom with pips

Anyone have insight to why the differences and when used?

Thanks

[Mk VII]

It may have represented reduction in machine time, or cost, or both.

The list of machining operations at Savage makes no reference to manufacturing the magazine at all, so they may have pushed it out to contractors, and the different types may represent contractors' alternatives based on the machinery in their possession.
Another telegram when Savage-Stevens production was ending makes reference to 90% of parts having been subcontracted.