Just a reminder that while the snacks and parlors had single arm pans, the full coaches had Stemmann [ I think I spelled that correctly, maybe one M ] pans that were 'diamond shaped but with a single arm on each side'. The original Jersey Arrows [ PC 100 class ] had em too. I don't know of an 0 ga source.
Also, a small but very visible detail: the cars with "The Fastest Phone in the East" [ the snacks and parlors ] had the white phone aerials on top.
Best regards, SZ
PS Due to catenary wave considerations, the cars on the NEC were operated in back to back pairs, with the trailing pan raised; there was a hard wire [ eg, bolted connections ] link between the two pans.