Johnny, thanks for the tip on the tar substance...
I'm ordering two transformers: MSD 8222 and another which is proprietary. The supplier [omit] provided the data to support a "Bosch-Black" likeness with the tar; the chart data is downloadable once you've purchased the coil from them. This coil is also offered by Stoddard but they don't provide any data that adds value to the converstation.
Zoom in on the side profile of the picture and you will see the manufacturer of the proprietary transformaer.
https://www.*************/sic60250201-sic-602-502-01.html
I"ll post my decision on whether I went with the (1) MSD, the (2) 44-year old black Bosch coil, or (3) the new "proprietary" one.