So, it turns out we're not making a 16 after all.
I didn't look closely enough at the picture Himself sent me of the Worsley Works etches and was left red-faced by a correspondent on our Facebook page who pointed out that what we had could only be used to make a model of 15 in its current ornate Victorian condition.
I looked again and the penny dropped with a clang! How could I not have noticed the big windows in the ends or the fancy covers on the frames.
Unfortunately, as you can see, Himself had already started to put it together so now he's got no choice but to try and replicate all the intricate gold leaf lining on the carriage.
I feat the air is about to turn blue...