Thanks for posting the pix, Larry. Here's some info on the Lucas #104 cowl mirror assembly:
Jeff Gagnon purchased one of our #104 mirror stems and compared it to an original he had, and found a slight size difference.
Since all of the original OE samples we had came from Lynn Park, and after checking the ones on his cars (Chad Everett's CSX 289, Dirtbag, etc for the #104, El Cid, etc for the #103) and all matched, Lynn suggested that's what we go with. More comparisons with CSX 2472 & 3151 (427 narrow hip street car, history known since new).. all the same, no difference.
The pix above in the comparison show the OE #104 from CSX 2442, and ours. The OE mirror stem has the yellow tape around it for ID. As you can see, pretty much identical. Within a few thou all around.
But Jeff's OE stem was marked as a #104, but was slightly oversized, his comment as posted earlier in this thread. He sent pix to me, sure enough.. a difference. He got the part from Lynn Park as well, more puzzling. Then I caught something in the close-up pic he sent yesterday of the base. A '75' marking in the base the others don't have. It's to the left of the 'Lucas No 104'. All the markings inside the base are not as deep as the others we used for 3D modeling.
That got me thinking about the die cast mold Lucas had in production all those years. The #104 was an off-the-shelf Lucas item used on a few cars, and probably popular at one time. So here's a possible explanation, not proven but likely. Die casting material is Zamak, aluminum and
zinc.. 'pot metal' to most people. It's very abrasive to the mold, so mold life is limited compared to say, plastic injection molds. Since the cavity was marked '75', I think that was the year the mold was overhauled. The slide, locks, etc. were probably shot and they repaired them to carry on, instead of replacing the mold. That would explain the slightly larger size, as they worked out any pitting and re-polished the cavity. That would explain the shallow engraving on the slide that forms the cavity inside the base.
Again, just a theory based on die-cast production reality. And the Brits never threw anything away : D
Dan, feel free to add to this : )