Westwind Interface Card
On a recent K10 that I bought it had a 50 pin connector hanging out the back.
I suspected that it might be some type of SASI or similar interface.
AD
From MicroCornucopia April 86

Other Files
http://www.bitsavers.org/bits/Osborne/Osborne1/Drive_C/Drive_C_-_Users_Manual.pdf

