To be fair. Cap G was not the first. Nor was Barry Gross.
Who was the first Ed??
I did not even know Barry Gross cast that way.
Vertical casting has been done for decades.
I believe buttons are still made with vertical casting by some manufacturers.
The resin is cast in long lengths, think 10', and then after being knocked out, they run through a slicer to be cut to the desired thickness.
There is more to the process to finish the slices into buttons, but that can be searched.
Research Bakelite and Catalin. Their rods were cast vertically. The process is still used in other countries that still manufacture Bakelite.
Model makers use vertical casting and use vent holes for escaping air, along with vibration to help the air escape from the small areas to be replaced with the resin for a solid cast without voids.
There are many things in life that is new to a group, i.e. pen makers, but has been done for many years before it was discovered by someone else to be recycled as a new idea.
We used to use a slightly more sophisticated set-up for vertical casting 25 years ago, at a manufacturer I worked for, and it's still being used today.
Something new, isn't always new, but rather just new to the individual(s) that recycled the idea.
MERRY CHRISTMAS!