I've been trying to work out the variations in this stock, with a view to printing some of the missing parts. It's complicated, of course.
The first of the coaches arrived in 1894. These had 16' wheelbase whereas the kits have 15'6", so the 1894 batch can be ignored.
There were more batches in 1897 and the kit I'm building is supposed to be one of these. In this year, the wheelbase changed to 15'6".
There was clearly a batch in 1898, as per the builders' photo posted above by William.
Finally, there were batches in 1900 and 1901, in which the brake-3rds had two compartments instead of three, were electrically lit from new and had Spencer's patent rubber pads for secondary suspension (i.e. J-hangers instead of T-hangers). These batches include the sub-set of brakes with lower birdcages.
Note that the 1898 coach in the photo also has electric light and rubber-pad suspension. Gloucester have highlighted these fittings in white, so presumably they were novel. The HMRS drawings that seem to match (so far as I can tell from the on-line thumbnails) show the older fittings, so I'm guessing that the spec was changed while these coaches were being built.
The 1987 brakes were in two series, one with steel underframes and electric lights and the other with wooden underframes (flitched?) and gas lights. The electrically-lit ones were said to have jumper cables dynamos but no batteries.
Finally, some of the coaches are known to have been upgraded for faster running in 1906 and 1907. The note in the kit instructions refers to new axle-bearings, but I suspect that the riding improvement was obtained from fitting the rubber-pad suspension. The brakes noted as upgraded are all in the wooden-framed, gas-lit batch of 1897.
At this level of complexity, and lacking photos, I'm inclined to put it down and leave it a while...but that's how I came to have a cupboard full of 1980's kits, so some resolve is needed.
Therefore, best guesses:
[*]All coaches built with gas lights were built with T-hangers.
[*]All coaches built with electric lights were built with J-hangers.
[*]Coaches with wooden solebars were flitched so that they look the same as the steel-solebar kind from the outside.
[*]Coaches with suspension upgrades in 1906/7 would have been initially in sets where all coaches had this feature (else why bother changing?), but coaches built with the newer suspension could appear with old-suspension vehicles.
[*]Gas and electric lighting could co-exist in the same set, but beware the jumper-cable arrangements: electric brakes of 1897 could only be next to an electrically-lit coach.
I need to print T-hangers for most of my train, which will be old-style. I shall eventually build alternate, 1901-pattern brakes to so that the train can be morphed into something that could go over the Met., so I need some J-hangers as well.
I need to print the brake rigging since the kit parts are too primitive.
I need some oval builders-plates since the kit doesn't have these.
The kit also lacks door hinges. I prefer to fit these at the end of assembly because brass ones mess up my glazing plan, so prints again. They will have 0.5mm spigots, to be glued into holes in the sides.
I may as well do the short buffer-guides that William requested, and in that case I should include the buffing cups, so that these fittings can be used on kits that don't have the branchlines castings.
I think that's it for the prints.