Shortly after posting about H 257 and H 258 never-seen-before(-by-me) ICs, I tried different search keywords and a datasheet popped up from the back of Internet.
According to that document SGS-ATES produced a series of High Level Logic I.C.'s designed specifically for applications in areas where noise is a hazard. The supply voltage is from 10.8 to 20V and they are compatible with MOS technology:
From the datasheet you learn that the suffix D1/D2/D6/B1 distinguishes between voltage+temperature range and case material. I think it was 1970-1975. Afterwards SGS should have adopted the standard naming for their IC line-up.
As already stated, contact me if you need those chips (H 257, H 258, H 202, H 203).
