[B B]

Other than the obvious, what's the difference and why?

 

[B B]

Anyone? It's the little things that drives me bananas

 

[WildBill]

Look at the tops(?) of them The length from the tops to those "nubbs( don't know what else to call'm) appears to be shorted on the left one

 

[mfuff]

My guess is different design due to different year of manufacturing.

 

[Steeltrap]

The spot weld fixture?

 

[whil e kioti]

Which one is from a newer model?

IMO... likely a manufacturing change for economic or for product improvement reasons.

 

[blackpowder]

The spot weld fixture?

My guess is the left one with 2 “spot welds” is the improved/newer version.

 

[Pa. Slim]

what are they in the first place? dont own a Marlin.

 

[Skooter]

They look like rear sight bases, without the elevator, v-notch, Buckhorn, etc.
That's the dovetail insert with the spot welds.
Probably bean counter mfgr. differences.
Might check here:
Marlinowners.com

 

[B B]

They look like rear sight bases, without the elevator, v-notch, Buckhorn, etc.

Exactly ^

One on the right is used and identical to the one that came off the gun.
One on the left is new.
Both are made for the make and model gun I have.
I'm replacing because the gun is in pretty good condition except some rust in the dovetail and the bottom side of the rear sight base that goes into the dovetail.

I'm thinking Steeltrap and Blackpowder's answer makes the most sense so I'll go with that.

Like I said it's the little things that drives me bananas