We've gone from manned obs to automated obs, max/min thermometers to digital probes, passive stevenson screens to fan aspirated shields, and lush wide fields to mulched Mars terrain surrounded by tarmac.
Once the ASOS period of record gets established enough, I think we're going to have to treat the pre-ASOS days almost the same way we treat the dead ball era in baseball. Cute stats, but pretty much tossed otherwise.