So what were nos playfields like when the games came out. Were they just dimpled?

Wms
all T-nutted & dimpled  if close to the end of the games run.

followed by dimpled only

then thirdly  not dimpled ( these were usually the WMS rejects that didn't make it as far as the dimpling machine.  or they had started a new pf/game and had loaded a new dimple plate

Sterns are at lest dimpled (as they do theres in house)