Zinc Chromate back in the 30’s was very expensive,….it was primarily used in the aircraft industry for protecting aluminum aircraft panels. Not sure if Lionel used that technology back then or not, I’d never say never, but unlikely would be my guess,….I don’t think toy manufacturers bothered with primers when producing toys, ….I don’t recall even seeing a primer coat on any vintage tinplate I’ve ever stripped,….now what they sprayed on the 700K in kit form, I can’t say,……but again, if you’re looking for a high end quality restoration, I’d talk to your local automotive collision/paint shop and see if they can help you with the project,…..bottom line is, you get what you pay for ….if it has a satin sort of almost semi gloss finish, automotive base coats without any clear coat can duplicate such a sheen,…..I’d ask if they could match the color seen on the inside of the tender shell if that’s the desired color/sheen…..a good shop can do that with ease, and shouldn’t be overly expensive especially if the work pieces are fairly ready to spray ….
Pat