On 2020-Jul-28, at 4:48 PM, Carlos E Murillo-Sanchez via cctalk wrote:
So, what would two chips marked
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
My guess is a house number 7-6987, with a 7306 date code, made by Fairchild.