3M "WhisperPrinter" (Trendcom 100) docs?

[Josh Dersch]

Picked this up for nearly nothing at a local recycler, it was too cute 
to pass up.  It's a 3M "WhisperPrinter" (model 1904AA), and it's a small 
(40 column, 4.5" wide) thermal printer with a serial interface.  It 
appears to work (runs a self-test if you hold the line feed button while 
powering on) but I don't know what the pinout for the interface on the 
rear is (it's a 20-pin header).

This looks to be a rebadged Trendcom 100 (which I can also find very 
little technical info about) used on a number of early home computers 
(Atari, TRS-80, PET).  Anyone happen to have a manual for this?

Thanks,
Josh