Well, here's my list of RTR wagons (all older products which IMO are the ones most in need of this sort of info).  The list of accuracy issues isn't exhaustive by any means, it's just the ones I know about! Possibly after some improvement + correction this list will be worth adding to the N gauge wiki.
Thanks to Pete33 and other forum members for help with IDing some of the wagon types. The Farish horse box (not the new Mk1 one) is a type I'm still not sure about. There are a lot of types from the pre-grouping era with a very similar appearance and door/window layout.

Peco:
5-plank open - LMS 10t open wagon
7-plank open - LMS 12t mineral wagon
Butterley steel open - Prototype (only one built) 14t open wagon built by Butterley in 1940
Plate wagon - BR 22t plate wagon, Diagram 1/430
Bolster wagons - BR 26t bolster wagon set, Diag 1/410
Twin bolster wagon - BR 21t double bolster wagon, Diag 1/415
Tarpaulin wagon - BR ferry open wagon, Diag 1/055
Tube wagon - BR ferry tube wagon, Diag 1/449 (body too short)
Standard box van - GWR 12t ventilated van
Refrigerated/banana van - SR 10t banana van
Cattle truck - BR standard 8t cattle wagon, Diag 1/353
Pallet van - BR 22t pallet van, Diag 1/235
Parcels van - BR 12t Insulfish/SPV parcels van, Diag 1/801 (body too long)
Conflat - BR 13t container flat wagon, Diag 1/069
Peak roof wagon - RCH 10t peak roof wagon
10' tank wagon - RCH 1927 tank wagon
15' tank wagon - BR 45t tank wagon
LMS brake van - LMS 20t 10' brake van
LNER brake van - LNER 20t 10' brake van
SR brake van - SR 25t 16' brake van (body significantly too long)
BR brake van - BR standard 20t brake van, Diag 1/506; also produced in LNER livery

Graham Farish:
5-plank open - SR 12t open wagon
7-plank open - LMS ex-NSR 15t loco coal wagon
Steel open - LMS 16t steel mineral wagon
Box van 1 - LNER 12t van
Box van 2 - SR 12t van with irregular planked sides (inaccurate roof shape)
Cattle truck - LMS large cattle van
Fish van - LNER ex-GNR fish van
Open hopper - Non-prototypical design based on the Presflo mould
Covered hopper - BR 20t "Presflo" hopper wagon, Diag 1/273
Tar tank wagon - Charles Roberts 8-12t rectangular tank wagon
Horse box - not sure
SR brake van - SR 20t ex-LBSCR brake van; also produced in LMS and LNER livery
GWR brake van - GWR 20t brake van "Toad"

Minitrix:
8-plank open - RCH 1923 8-plank 10/12t P.O. wagon
Steel open - BR 16t mineral wagon, Diag 1/108 (overscale body)
Box van/Shocvan - BR standard 12t goods van, Diag 1/208
Tank wagon - RCH 1927 tank wagon (some detail differences to Peco model)
BR brake van - BR standard 20t brake van, Diag 1/506

Lima:
7-plank open: RCH 1923 7-plank mineral wagon
Steel open - BR 16t mineral wagon, Diag 1/108
Box van - BR standard 12t goods van, Diag 1/208
Horse box - GWR horse box "Paco", Diag N16
Siphon bogie van - GWR Siphon G, Diag O33
BR brake van - BR standard 20t brake van
GWR brake van - GWR 20t brake van "Toad", some detail differences to Farish model (earlier prototype)

The Farish SR brake van is a late LBSCR design (same as Hornby did: http://www.kmgmodeltrains.co.uk/images/022.JPG ) and reasonably accurate. More prototype detail in Terry Gough's article in RM May 1971 which I can't at easily find at the moment!

The Lima Siphon G is dia. O.33, built in many lots from 1930. There were several different types of bogies used, the earliest batch using the 7' plate bogies (Dapol spare NBOG1 http://www.modelrailwaysdirect.co.uk/Dapol-NBOG1-Pair-of-Short-Coupling-Bogies-for-B-Sets/). The horsebox is dia. N16 of 1937.
I always thought the body of the Lima GWR brake van was rather better than the (admittedly earlier) Farish version, though the chassis suffered from the usual Lima fault of excess ride height. Technically the Lima version is an earlier version as the upright angles on the body are the type that tuck under the lower edge of the body whereas the old Farish one has them continuing straight down over the solebar (the new Farish model seems to be the same as the Lima type). Prototype examples:
Lima & new Farish: http://paulbartlett.zenfolio.com/gwrbrakevan/h21be9cf9#h21be9cf9
Old Farish: http://paulbartlett.zenfolio.com/gwrbrakevan/h29ce7d03#h29ce7d03
Note, however, that the underside of the verandah end on the old Farish model is wrong in being taken across flat - that needs altering (carefully!)

Quote from: BernardTPM on February 19, 2014, 06:47:33 PM
The Farish SR brake van is a late LBSCR design (same as Hornby did: http://www.kmgmodeltrains.co.uk/images/022.JPG ) and reasonably accurate. More prototype detail in Terry Gough's article in RM May 1971 which I can't at easily find at the moment!

Back in the seventies I probably had that very issue, along with a stack of back issues from the sixties. It's a shame I don't have them now because I can't find a single thing on the Farish model online. There are plenty of photos showing a two-side-window version, but nothing at all with a single side-window that matches the Farish version.

Quote from: BernardTPM on February 19, 2014, 09:44:05 PM
The Lima Siphon G is dia. O.33, built in many lots from 1930. There were several different types of bogies used, the earliest batch using the 7' plate bogies (Dapol spare)

The Dapol Siphon chassis is also a pretty much perfect fit for the Lima body and as well as coupling and running way better its sometimes cheaper than a pair of spare bogies

Quote from: EtchedPixels on February 21, 2014, 10:36:50 PM
The Dapol Siphon chassis is also a pretty much perfect fit for the Lima body and as well as coupling and running way better its sometimes cheaper than a pair of spare bogies

Trouble is, the underframe detailing is wrong for the later Siphons which had battery boxes rather than gas cylinders. A few did have the 9ft plates (some even used some 8' 6" w.b. bogies which I assume were recovered from the experimental articulated stock when it was rebuilt to conventional form) but the most common type under inside framed Siphon Gs are the Pressed Steel type. In fact the bogies for the new N Gauge Society K41 would be perfect, though as the K41 couplings are going to be body mounted (on a close-coupling mech) it wouldn't be an easy option.

Has anyone managed to work out how accurate the Dapol wagon is and which diagram it matches?

Dapol Cat No 2F-071-005, SR 10T 7 Plank Wagon Diagram ? No 37423 Built ?
Alternative running numbers: ?

After a very long search, I think I might have pinned down the SR conflats being offered by Robbie's Rolling Stock. The Conflat B and Conflat S seem to be Diagrams 1382 and 1383, although 1382a and 1399 might also be viable. The trouble is that there seem to be no photos online that can be matched up to the model form.

http://www.robbiesrollingstock.co.uk/images/Containers/SR_ZZ_Type2.jpg

All I found, on another forum, was this:

Diagrams 1383 1382* 1382A 1399 were built as 'conflats'. Although only 1382 1382A and 1399 could reasonably be classed as conflats as they were built post 1932 (after it was found 'necessary to build special wagons for the conveyance of containers).

There is a brand new Diagram 1382 'Conflat B' on page 47 of 'An Illustrated History of Southern Wagons'.

However on page 53 there is a photo of a '1399' labelled 'Carfit S'.

So they probably went from one to the other over their life.

I didn't necessarily mean to suggest that the function of container carrier predated use as carriage trucks, just that at least some (most???) of these flats were originally built for container traffic.


*some 1382 wagons were built with in 1931 (at the same time as the 1383 wagons - I know a that doesn't make sense but that's diagram books for you)

That's about as accurate as I can hope to be without having the reference book itself. So we're left like this:

Robbie's Rolling Stock Cat No C25, SR 12T Conflat B Diagram 1382? No 39796 Built 1930-31? Carrying a Southampton Docks container.
Alternative running numbers: ?

Robbie's Rolling Stock Cat No C26, SR 12T Conflat S Diagram 1383? No 39372 Built 1930-31? Carrying a Type T2 Zigzag SR furniture container.
Alternative running numbers: ?

Robbie's Rolling Stock Cat No C27, SR 12T Conflat S Diagram 1383? No 39940 Built 1930-31? Carrying an 'insulated for perishables' container.
Alternative running numbers: ?

Robbie's Rolling Stock Cat No C29, SR 12T Conflat B Diagram 1382? No 240728 Built 1930-31? Carrying a Type B door-to-door container.
Alternative running numbers: ?

Robbie's Rolling Stock Cat No C30, SR 12T Conflat B Diagram 1382? No 39705 Built 1930-31? Carrying a Type M ventilated road-rail container.
Alternative running numbers: ?

Robbie's Rolling Stock Cat No C31, SR 12T Conflat B Diagram 1382? No 39777 Built 1930-31? Carrying a Pickfords Removals container.
Alternative running numbers: ?

This one took a bit of work, but I'm pretty sure it's correct:

Dapol (all models), SR 14T Covcar/CCT Van Diagram 3101 No 23xx Built 1938. 2+2 plank arrangement but doors are even planked, matching this to a single batch built at Ashford and Eastleigh in Nov-Dec 1938. Dapol numbering and lettering is post-Nationalisation and needs to be removed and reapplied in different locations for SR.
Alternative running numbers: 1731-80