Buttonholes in paenula?

[Caballo]

Went round today to see the original in the Museum of London (the joy of working in the City) , and the "roundels" are clearly on the seam, with distinct cloth folds either side.The parallel lines at the bottom to me look like a thread or leather horizontal stitch to hold the paenula at the the top of the "W".
The options appear to be:-
-Two round brooches
-A button hole (? unlikely given positioning over the seam?)
-Round button and very short leather loop (NB: no trace of ANY loop on the sculpture that I could see)
-Mistake by the sculptor

I buy Crispus' idea that some were fully stitched, but some clearly had fastenings. The question is how....????

Cheers

Caballo