I authored those files so I could render the Seventh Edition manuals as PDF in 1998 (long after I had departed the Labs). As pic did not exist yet (Kernighan had not written it) there were never any original pic files for these documents. I do not know what 1127 was doing to publish diagrams at the time. The Bell logo I did directly in postscript so \(bs would render. The logo was originally it's own custom "character" just like an A, B or C, on the phototypesetter's optical font wheel. You can see what they look liked from the v7 PDF manuals -- In Volume 2A (http://plan9.bell-labs.com/7thEdMan/v7vol2a.pdf) bs.ps is on variety of pages such as 129, 130, 216 ms.pic is on page 127 make.ps is on page 282 In Volume 2B (http://plan9.bell-labs.com/7thEdMan/v7vol2b.pdf) implfig1.pic is on page 162 implfig2.pic is on page 168 these are the PDF page numbers (where the title is page 1)