Aren't they a 2 way system with a 10" woofer and black grilles? If so, they are from the mid seventies. They replaced their ADC's 303 speakers, which were essentially the same thing. both were pretty decent with a fair amount of bass and a nice crisp (but not overbearing) mid/high end.
ADC was a well known brand then and specialized in phono cartridges and a few speakers. Theit 404 was probably the first mini-speaker on the market and their XLM/VLM pono cartridges were considered among the best available, even if a bit delicate.
Later in their lifetime they became more known for consumer level graphic equalizers and by the end of the seventies they sorta began their fade into oblivion.