On 2020-Jul-28, at 4:48 PM, Carlos E Murillo-Sanchez via cctalk wrote: > > So, what would two chips marked > > F U6A7709393 > 7043
F : Fairchild U : monolithic device (as opposed to e.g. hybrid) 6A : package, DIP (6), 14-pin (A) 7709: circuit/function code. As Jay suggests, a 709 op amp. 39 : temp range, 0::+70C for linear types 3 : I don't know, in 1966 this was a reserved-for-future-use digit position. 7043: date code of course. I've seen other analog ICs from Fairchild similarly labeled, e.g. U5B7741393 for a 741 op amp. > and > > F 7306 > 7-6987 My guess is a house number 7-6987, with a 7306 date code, made by Fairchild.