Here is a post I found here on old gas that appears to answer my question. From carolinatraveller
Here is the story on the sign. In 1956 Sun Oil began experimenting with their Custom Blend pumps. The first group, found only in Florida, use a pump plate similar to the standard one in use at the time, the small Blue Sunoco diamond and the porcelain vertical stripes. Only difference was that this Blue Sunoco diamond had an extremely thick blue border. I have only ever seen one of these, and I have it in my collection. The second generation Custom Blend pump plate is the porcelain blue upper and lower section Blue Sunoco plate, with studs on the back. These were in common use by 1957-58 and used through about 1970. The older signs not immediately removed, but new Custom Blenders installed after about 1970 feature a decal of the then current logo, with the diagonal arrow, with only the word Sunoco, not blue Sunoco. These are the only pump plates ever used on Custom Blenders.
So what about the 200, 200X, and 190 plates? Well, while every Sunoco station was equipped with a Custom Blender pump by about 1958, the new blenders were not installed in every fueling position. Older pumps, usually the old M&S80 series pumps that had been in use since the late 1940s, were repurposed to sell only Sunoco's regular grade, which was Blue Sunoco 200. The older pumps that remained in use in the 1958-1965 or so era displayed the Blue Sunoco 200 plates, or the 200X for a temporary product promotion. The 190 plates, which were all tin as far as I have ever seen, were used in this same manner when Blue Sunoco 190 was introduced as a sub-regular grade, in 1961 I believe. Anyway, by 1965 or so most Sunoco stations had nothing but Custom Blender pumps, in every position, and the older pumps, along with the 200, 200X and 190 signs were no longer in use.