It is really LM108 and LM112 (internally compensated) and there is absolutely no trick there. It's got 1nA enter bias that's fairly steady with temperature as in the majority of bipolar opamps since β really improves with temperature. Later on iterations like LT1008/LT1012 or OP97 pushed it down to A https://pin-diode-switch66666.creacionblog.com/33995861/the-smart-trick-of-coaxial-switch-that-nobody-is-discussing