Hi Michael, this is the ScotchKut Double Outline, or more than likely a digital font based on the original plastic alphabet. There are three versions of the font, which differ depending on the size of the original letter sets. It is unclear whether the version of the font used for the surname is based on the largest or medium-sized alphabets, but the names and dates appear to be based on the medium sizes.
The MLC has created versions of the font to match the medium and large sets of the fonts: https://www.monumentletteringcenter.com/product/mlc-scotchkut-double-outline-medium-large/
As well as the small sets: https://www.monumentletteringcenter.com/product/mlc-scotchkut-double-outline-small/