Rear Wheel Chain Adjuster Blocks Question

[42barab]

Attached pics show two seemingly different types chain adjuster blocks.  The left pair have a rough "sandcast" finish and the right pair have a smoother finish. One other notable difference is the back of the blocks, where the left pair have a continuous arc and the right pair have three flats.  Is one correct for the sandcasts (this one is 2659) and one is not; or were they both used on SC bikes?

[Don R]

 Good question, I have one bike that is for sure original, sandcast 5511, the 14,100 diecast has a different swingarm although it was from an earlier frame and my late K0 I think is original. If I get to the shop and can get between the bikes I'll try to compare them.

[Rddmm2]

a pic from 6806.  The parts have since been cleaned up, but a similar rough finish.