got this BASF mono beauty today. getting this was absolute coincidance, i wasn't looking for it, it found me:
The FM buttons might put it after 1977? I don't know when that technology started, my little multi-band radio had individual tuners for the "presets." The only BASF BBX's I can find are in the EU but that looks like it would look great on display, especially with the red lit dial.
radiomuseum.org dates it 1978, with a questionmark: https://www.radiomuseum.org/r/basf_d2100d_210.html