David...
To me the R-12 version is appropriate for work done around here. Am using very expensive machine tools that work off of computers. They accept input in pen plotter language, as do many of the other manufacturers today. R-12 was based directly for pen plotters, and there is near zero problems as to interface exchange, iff'n you can see the drawing on some version of R-11 or R-12. If you can see it, then the work will go smack over into some sort of original HP-GL language.
If any error message comes up, such as a non compatible or missing font, then it will fail. Which is why perhaps so many of the computer based machine shops in the Los Angeles area readliy accept projects which can be seen in R-12.
The project work may all be initially created in late model software, but then gets converted backwards. If a shop is using modern Autocad, they are also charging more than their neighbor for same work. Switching to a more modern version of Autocad is little expense for them. Switching out a whole million dollar machine to be compatible for one year, that becomes expensive and costs them jobs.
So, keep the R-12. Write it to sme safety disk, but keep it handy.
Wm.