When looking round a second-hand bookshop yesterday, I found this book on Modula-2:
I seemed to remember that there was some connection between the PDP-11 and the Modula-2 programming language, so I took a chance and bought the book for £1. I spare no expense on my computer history collection :-) Anyway, now that I've had a chance to check, I found this "The first Modula-2 compiler was completed in 1979 and ran on the DEC PDP-11" (taken from here). So it does seem like a worthwhile addition to my collection of PDP-11 related objects. This pleases me.
...and for the sake of completeness, here is the back cover too (even showing the original price tag):