While not perfect. An easy way to confirm the date my house was the nameplate radiator covers. The accessor office has it 5 years older, but looking at the abstract (Iowa has abstracts, which are cool. The property title and associated docuemnts go back to local indian treaties in the early 1800's). Another can be looking at things like cast iron covers on the old coal chutes. Agreed, that toilet and fixtures aren;t as reliable because in installed before the 20's they have usually been repalced by now. THings made starting in the 20's were a litle mor emoderns.
Previous home - 1968 single story Ranch/Colonial, 1200sqft - 11 windows
Current home - 1925 2 story Beaux Arts Neo-classical overlooking the Mississippi River, 3200sqft - 48 Windows