Whilst on the topic of vans, I've had a bit of a head scratcher this last week.
Someone shared with me a Ken Werrett drawing of a ventilated GE dia.15 that was also fitted with vac brakes, and was drawn in the post-1912 livery with large V markings at each end (which fits, as the measurements were taken in 1917). An interesting prototype, by all accounts, except the running number was GE 20732 - The very same number I'd used on my ventilated Dia.15, albeit, my van was not fitted. I'd used that number as it is the one provided on the powsides transfer sheet, which, it seems, take influence from the Ken Werrett drawing, as the style of the V (split into two lines at the bottom) is identical to that as drawn.
My concern, however, was that whilst I could update my model to feature vac brakes, previous discussions here and elsewhere have made me skeptical as to the accuracy of his drawings. Indeed, the livery for GE 20732 is given as cream sides and black ends... Close if you squint, but not correct.
So I went down a rabbit hole of trying to find photos of ventilated Dia.15 vans (as
@Herb Garden will verify through gritted teeth, I'm sure!). This led me to a photo found on Facebook, which is not credited, nor has any information to supplement it regarding location, date etc.
It shows, what I make out to be GE 20791, interestingly with a dark solebar, instead of the usual French Grey. The problem with this? My unventilated Dia.15 had been numbered 20791 after I lifted that number from the Railway Heritage Register (allegedly that of an unventilated example to be found at the Mid Suffolk?).
Long story short? I've renumbered both!

GE 20960 is based on a survivor currently at Mangapps and GE 20393 is, I confess, me committing the cardinal sin of modelling a model, for that number is one of the ones used on a van in the model collection at the NRM!
They're now going away before I find out anything else unexpected!
- James