Just focus on flat numbers versus round ones and closed numbers versus open ones and you will get it right regarding era of production.
Rolex had many suppliers and some discs from the same era came brushed, mat, shiny or not with thick numbers or thin ones, position marks or blind,
inner circles or not...you name it.
Just have a look at pic 1 all for 1575 but also for 1565 and 1570. Same era but all different when looking closely.
I keep some boxes of date discs of every kinds (pic2) because some collectors have precise needs even though I really think it is silly.
For DD's (pic 3) it was even crazier as the Pantone range of colors was simple madness imo (look at the choice of colors for WG/PLAT/YG).
Sorry for the poor pics as usual. Edit typos