Denny- I'm not an expert, but I think "Spanish Grain" refers just to the vinyl's texture... and I think you are correct, the grain is significantly pronounced. My '54 3104 has this brown grain textured vinyl on it--but it is very beat up and underneath ripped ugly blue vinyl (see
here ), which is why I want to re-upholster everything.
I did find this definition on the web, so take it for what it is worth: "Spanish Grain - Finish produced by embossing on fancy or upholstery leather a modified natural grain which formerly was produced by drawing or striking a hide or a skin in a strong tan liquor to shrink the grain, the result being to form a particular pattern on the surface, owing to unequal shrinking of different portions."