I suspect the original finish has been removed from you arm. It looks like the early Odyssey Engineering RP1 design from 1980. It was offered in various finishes, some in a black lacquer, others with custom colours, others chrome plated and/or anodised.
That's interesting, I had wrongly assumed they were all gold over brass and anodised ali, so this one has been stripped eh?
your arm appears to be a refinished RP1-P from 1981 which had a triangular base (later circular) and separate armrest, and had shims on a solid pillar.
Yep I recognise that....I have the shims and the base as you describe. I can see how that would have been easier to produce.
With the base in the photo you don't need an eccentric mount (which for me, originally, was a simple way of getting an adjustment like SME without having to mill out the slot and pillar mount...) therefore you don't need slots in the headshell, as you can vary the mounting distance to suit the true effective length (which used to vary depending on which cartridge was used...)
Can I clarify something regarding slots in headshells. The arms that have them are designed with a fixed mounting distance, ie the lateral pivot to spindle distance is unadjustable.
Isn't hindsight a wonderful thing it does seem to work pretty well, however, and having mounted it I am glad the headshell slots are there from the weight/mass perspective, it would have been too heavy otherwise...I would have had to make the headshell shorter instead - whomever said 'engineering was the art of compromise' was spot on.
By the way, its a great arm and I definitely think its been worth the effort to ressurect it.