Thanks to B 9 for converting these images into a PDF.
I've typed the contents of the card into a text file - see card.txt (UNIX-format text file - open with Wordpad if you're viewing it in Windows).
The card says 'TRS-80 MODEL III DISK SYSTEM' at the bottom of the first side, and unfolds into five panels. The leftmost panel reads 'Disk BASIC Statements' and starts with CLOSE. The panel to the right reads 'DEFFN'. Panel 3 says 'PUT b, record number' at the top. Panel 4 reads 'Disk BASIC Error Codes' and starts with '51 Field Overflow'. Panel 5 is the front of the card and has a small picture of a TRS-80 and the words 'TRS-80 (R) MODEL III MICRO-COMPUTER SYSTEM' and under that, 'Start-Up'.
The first panel on the other side of the card reads 'TRSDOS Commands and Utilities' and starts with 'APPEND'. Panel 2 starts with 'DIR :d(INV, SYS, PRT)' and panel 3 with 'PATCH file'. Panel 4 says 'TRSDOS Error Messages' (the first is '0 No Error Found' - I've never had that one appear!). Panel 5 is headed 'Disk BASIC Functions', starting 'CVD(str)'. At the bottom is a stamp from the shop where the card was bought: Devitt Electronics in Barnstaple. I think that shop is now a tanning salon, sadly! Mr. Devitt was a friendly and somewhat eccentric man who called all of his computers 'she' and took great care of them. I used to go there and play Flight Simulator (we're talking Flight Simulator 1 here!).
I'll add other documentation as it becomes available (meaning, as I scan it - who knows what goodies are hidden in these piles of paper?).
I added the following JPEGs were added on 21-Jan-08.
I had many problems processing these, due to my image processing software's insistence on saving imported JPEGs as resized, transparent images. These will need a little bit of processing.