It is LM108 and LM112 (internally compensated) and there is de facto no trick there. It has 1nA input bias which happens to be pretty stable with temperature as in the majority of bipolar opamps mainly because β truly improves with temperature. Later on iterations like LT1008/LT1012 or OP97 pushed https://ricardommhfn.theobloggers.com/40444758/what-does-pin-diode-switch-mean