Beware counterfeits. Those plates backmarked "Walker China" and "Alco Standard Corp." are all reproductions. Alco Standard Corp (unrelated to Alco Locomotive) bought Walker China in 1967, three years after the NKP was merged into the N&W! The date codes seem old, but one must add the code number to 1922 to get the date of manufacture (i.e. 5-49 would mean 1971!). Those stamped "Alco Standard" are much more common than the authentic pieces (repros usually are), and they are rarely disclosed as such when seen for sale. Walker pieces NOT stamped "Alco Standard" are probably authentic (but ought be subject to normal scrutiny).
(Note: The use of the word "counterfeit" to describe this china is not meant to imply that it is "good" or "bad" - for our purposes, the intentions of the counterfeiters are irrelevant. Authentic dining car china was made to be dining car china, counterfeit china was made to look like dining car china. Well done or not, it is not authentic dining car china, and if it is not clearly marked as a reproduction, then it is counterfeit.)