These .IMD files were supplied by Jonathan Chapman, and are images of "diskettes ... 
acquired from the estate of Tom Kirk, who worked at a number of east coast/New Jersey 
tech operations in the 70s and 80s, including Bell Labs and Technical Design Labs."

To date, I have been able to extract the contents of 24 of these using ImageDisk's
disk-analyse and cpmtools' cpmcp using the ibm-3740 disk definition. Though Jonathan 
said "These are all CP/M Standard Distribution  format, 77 tracks of 26, 128-byte 
sectors, single sided, single density", I have been  unable to access data from the rest.

Files here are as follows:

tkirk_sigm.tar.gz - the original image collection, as supplied by Chapman
*.IMD             - the original IMD images
*.TXT             - technical specifications on the images, as reported by ImageDisk
extract           - a BASH shell script for extracting the contents of the IMD images
extracted/        - the contents of those images that could be extracted