Like the 11th Doctor’s “scales” waistcoat, his velvet waistcoat had two different sets of buttons over the course of its on-screen appearances, and like his “anniversary” waistcoat, the velvet waistcoat had six buttons.
The first buttons to be seen on the waistcoat were gold “perfume” buttons, with what may have been a small bit of fabric in their center.
His velvet waistcoat also had these buttons in the publicity photos for that special, which were high-resolution for us to see them in greater detail.
Fast-forward a half-dozen episodes or so, and the next time we saw the velvet waistcoat, the golden “perfume” buttons had been swapped out for black passementerie buttons.
These buttons appear to have been ⅝” (15mm) in diameter, also known as 24L, but this is their total diameter, not just of the base onto which the button is constructed.
These were also the same style passementerie buttons used on the Eleven’s “scales” waistcoat – but black, of course.
Oddly, for the prequel to the season finale, “She Said, He Said,” the Doctor’s waistcoat again had the golden “perfume” buttons.
In the actual season finale, though, his velvet waistcoat had the black passementerie buttons.
Despite his waistcoat having had black passementerie buttons the entire episode, after he jumped into his own time stream to rescue Clara, the buttons switched back to the golden “perfume” ones!
Doctor Who has a built-in defense against continuity errors, though, especially when there’s a lot of weird “timey-wimey” stuff going on … and I’d say that the Doctor being the third entity to jump into his time stream (with the launching point being a dead TARDIS at the alleged location of his future death) definitely counts!
In any event, for the velvet waistcoat’s final appearance, the black passementerie buttons were back again.
The waistcoat had black passementerie buttons in the publicity photos for the final two episodes of the season, as well as “The Time of the Doctor.”
Here are some close-up screencaps and photos of the passementerie buttons.
The velvet waistcoat formerly on display with the “Snowmen” costume at the Doctor Who Experience had these black passementerie buttons.
The buttons appeared to all be aligned horizontally (with none offset from center).
However, this may be an optical illusion; the top button was probably offset a bit to help cinch the upper front of the waistcoat toward the chest of the wearer. (It usually is on men’s waistcoats.)
Using the ⅝” (15mm) passementerie buttons as a reference, I extrapolated a button spacing of approximately 2 ½” measured from button center to button center (or from buttonhole to buttonhole).
Also note that these buttons were horizontally positioned so that their outer edges were flush with the inner edge of the decorative trim.
Using the ⅝” (15mm) passementerie buttons as a reference, we can also ascertain that the golden “Snowmen”/”perfume” buttons must have been slightly smaller, perhaps ½”.
One final observation, perhaps regarding the buttons: at the end of “Nightmare in Silver,” observe this curious line of what appears to be vertical topstitching just outside of the buttonholes.
I’m not sure if this was always there and only visible because of the specific lighting/angle of this particular shot; I hunted for more examples of this and found a few hints of what might have been topstitching; peruse the numerous examples provided in this analysis and you may, too.
If this was, indeed, a “thing,” perhaps its purpose was to secure the front facing to the front and stabilize the buttonhole area? It’s also possible that if this topstitch was always present, it was buried in the pile of the velvet and obscured with a brush, as Kenneth King likes to do.
On the other hand, it’s also possible that this topstitching wasn’t part of the intended waistcoat design and/or was only on this exact waistcoat, then nobody noticed or realized it in time before filming. Afterward, the waistcoat wasn’t used again, the stitching was removed, or additional examples have simply eluded me.
Make of it what you will!