I think one of the main ways in which the modern sets differ from the old sets is the pawns - the newer pawns are larger, have fatter collars are the tops are not round. The down side of the old pawns is that they are a lot more delicate, of course. Here is a picture to show the difference, both these pawns are from similar sized sets - a King and pawn from an the old Jaques set on the left, and from a modern set on the right:

Also, you sometimes get to see the grain in the ebony on old sets (hopefully you can see this in the old pawn above), I haven't seen this on modern sets

On the subject of the annoying lean I recently corrected a lean in a K&Q from a 3 3/4” french staunton by cutting under the collar from the high side with a jewelers saw (if you know what I mean). Seems to work ok. As yet I have not tried to disguise the cut line with wood glue/boxwood paste. Wouldn’t necessarily do it with a valuable antique set but for old Lardys etc it may be a solution. Have used the set and tried to break the join with a little force and so far it seems fine. I used CA and applied to the gap with a plastic straw before clamping straight for 24 hrs.

Will you be posting any photo's of your Jaques sets ?
OK you've twisted my arm ... here is a club size set from 1875-80 (I think):