It can be LM108 and LM112 (internally compensated) and there is absolutely no trick there. It's got 1nA input bias and that is reasonably secure with temperature as in many bipolar opamps because β truly enhances with temperature. Afterwards iterations like LT1008/LT1012 or OP97 pushed it right down to A: https://mylestsmju.blogpayz.com/34266432/top-low-noise-amplifier-secrets