What I remember from my experiences with terminals and printers (the only display devices available at the time) from 1978-1980 was that the 0x7F <DEL> characte

What I remember from my experiences with terminals and printers (the only display devices available at the time) from 1978-1980 was that the 0x7F <DEL> character rendered as a checkered box. This correlates with (0xFF) Figure 5 in the article. This was common among all printers I worked with, Teletype, Epson, Okidata, TI, Printronix, and even IBM. Also all the Lear Siegler, Televideo, DEC, Hazeltine, terminals I used did something similar. Even the character ROMs in my Ferguson Big Board II, and Kaypro II used the same checkered box pattern.