Hello Adrian,
Maybe I'm wrong, but because the old, original moulds are still used, as I'm sure you have read, I don't think that there's a difference re the signatures. I've seen the engraved signatures and the pressed ones, and the only difference, to me, is the quality and finishing. The older ones are just more defined, as you've mentioned. I was in Mexico for work recently and I don't think I've ever seen that much of Sabino in one day, but every piece I've had in hand, felt and looked a bit rough and unfinished, visible and unpolished seams and as you say, without any detail in the moulding and was just not good enough to justify the price.
Therefor i think, the only way to be really sure is to handle the item in hand, from a picture it's more difficult but your gut instinct never lets you down.