The peg is the interesting aspect, and I do wish I could know what is going on in there. I haven't put a ruler to them,but it is on the large side, perhaps 1 3/4" and placement is the same on all of them, with all that end distance in the relish.

They have held up to time well (though one suggest some movement) despite some erratic repointing and parging over time, sometimes with portland in the mix, most of that and the predictable results happen lower down - I'd suspect the Ties are still bedded in lime mortar.