Colour (negative) film normally has a 'correcting mask' (giving it, typically, an orange colour) which is beneficial in the printing process. If you try to get black-and-white prints from such films you usually get poor results because the mask results in a 'washed out' look to the resultant images.
However in 1956 Agfa introduced Agfacolor CN-17 Universal Colour Negative Film, which didn't have the orange mask. That made the negatives look very much like those from B&W film and meant that the user could choose between (relatively cheap) B&W prints or (far more expensive) colour ones. The film remained in production until 1968.
Take a look at the edges of the negatives. It's likely that you'll see 'CN-17' there.
Sourced from some distant memories of photography in the 1960s, supported by this:
http://www.photomemorabilia.co.uk/Colour_Darkroom/Early_Agfa.html#anchorAgfa15o