The native datewheel position in a DG /ETA movement is 1mm right of the 3135. Most higher end reps have dials with a date window shifted left 1mm to match the Rolex position, and use a datewheel overlay (DWO) to shift the date numbers to match. However this is not always the case so you have to know what you are buying. There are still plenty of rep dials with unshifted date windows. If you buy an ETA dial with a shifted date window, it *should* fit the DW of the 3135.
KJ2020 perfect mate, i really appreciate you taking the time to reply. Perfect answer and has sorted my worry.
2824 dial on route has window shifted left and used an overlay on 2824. So date should line up, i can move dial feet so as long as its the correct diameter im good.