Well, the Pre-V and Pre-A dials are not really sandwich dials, QQ. Sandwich dials are two-piece dials - a lumed bottom plate and a top plate with the indices cut out to reveal the lume beneath.
The Pre-V/Pre-A dials are single-piece dials with deeply engraved indices that are then lume filled. The lume filling is shallow enough that it gives a similar visual effect to sandwich dials, however.