Uher 4200 Tape Recorder.
There were a family of similar high specification battery tape recorders in the Uher (W. Germany) range. I used a 4200 model from 1970 - the model number signifying 4 speeds and 2 tracks. It is a stereo machine so with just the 2 tracks the tape could only be used the once, you couldn't turn it over and run it through again (unless in mono mode). The 4400 had 4 speeds and 4 tracks on which you could turn the tape over and use again in stereo. The 4400 had a slightly inferior signal to noise ration, although I remember a Uher technician challenging anybody to actually hear the difference.
In many ways these battery (mains with an adaptor) tape recorders were the best available in the world at the time, they remained in front line performance for years and years. In 1999 I was interviewed at home by BBC Radio Hereford & Worcester - they used a Uher 4000 - even though it would have been around 30 years old. The one better battery recorder I recall from that era was the Nagra - but at around £500 they were just a pipe dream.
I still use my 4200 to play all my original train recordings, it is however showing its age a bit now and needs TLC to keep it going.
All the links below are taken from the July & October 1969 issues of Tape Recorder magazine.
Uher - Survey Of Battery Tape Recorders.