This mixer / amp came in 2 versions.
One version had a stereo option although you would need to link a slave amp to get stereo. I used to have one of these but no longer. I’ve included a picture of the one I used to have and you can see that it has a mono/stereo switch and stereo output sockets on the front.
The Bandmixer I do currently have is a standard mono version. It consists of 4 channels, each channel having 2 inputs, volume, bass and treble controls. There is no reverb, just a master volume slider, a slave output socket, and a stereo socket for linking an echo unit such as a Copicat.
The Bandmixer pictured has replacement slider knobs as some were missing when I acquired it and the others were used on my Reverbmaster.
Here is – a link to the WEM catalogue – showing the Bandmixer and its technical specification.