This is the thick, best piece:
It's a double buckle collar 2" 3/4 wide, with 3/4" stainless steel buckles.
This is how I stitched the buckles this time:
I consider that an improvement to the model, as now the buckles and the D are fastened in the same way to the main body. It measures 13" 1/8 at middle hole and it features a lighter padding, to keep both weight and thickness to a fair level.
These are the tag holder collar, made in rolled leather with a 5/8 buckle, and the training leash, 1/2" wide, with stainless steel scissors snaps: