The smart cards came into practice like 5-6 years back. And before that the owners has the passport books for the vehicles.
If vehicle has passport book, then check its used pages. All the previous owner details should be there on the book.
Each transfer has one sticker on passport book which covers its one full page
with details like name, father name, nic, chasiss, model, etc.
Also check the file of the vehicle, all ex-owners (as per book) must have their ID Cards and T.O. (Transfer order forms) attached in the original book. If some ex-owner is mentioned in the passport book but his NIC or T.O. is missing in the original file, then it means some documents are missing in the original file which is not a good sign.