The current design:
The idea arose while working on a new design for my personal business card. While the front is already inspired by technical drawings, I needed an idea for the back side, which so far had the printing company's logo on it as I got them made for free.
I figured it would be nice to leave it mostly blank to be able to add some notes. The first addition was a 5x5 mm dot array to allow for better hand-drawn straight lines.
I guess an isometric grid variant would also be neat for 3D sketches!
As an engineer, I quickly settled on a scaled-down and simplified version of the drawing title block defined by ISO norm 7200.
(Image above by Con-struct [CC BY-SA 3.0], via Wikimedia Commons.)
Some of the fields were removed, others renamed. Creative freedom applies to ISO norms, too! :-)
A frame with a simple 8x5 coordinate system helps when describing or referencing sections of the drawing elsewhere. This might be more useful for A4-size documents and larger, but it is there nonetheless.
I added the symbol for first angle projection, mainly as an aesthetic measure.