When Did N&W Begin Buying PL-3 Signals?

[NW Mailing List]

Is it known when the N&W first began buying the model PL-3 position light  signals (lamp housings,) instead of the original PL-1 versions (which were first bought in the 1920s) ? 



Union Switch & Signal Co. cannot tell me when they introduced the PL-3 modification !  (Too many buy outs, renumbering of drawings, cleanouts, loss of "corporate memory" etc etc etc.) 



If anyone would know the answer to this question, it would be someone on this List or in the N&W HS. 



-- abram burnett
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