[Radio Wrangler]

They will have used stencils, and may have worked at a large scale, photo-reduced to the print size.

Rotring ot Uno pens are more easily compatible with stencils than nib type pens.

The biggest contributor to the quality was care and time. Substances in short supply these days. A second factor is arty people now looking at a magazine page and deciding that the circuit diagrams need to be much smaller and less bold in order to 'not upset the balance of the page' An engineer would make them as large as necessary in order to be clear, because they contain the majority of the information.

David