I have previously discussed how railroads used milepost number places as an easy way to distinguish absolute from intermediate (ie permissive) signals. Like pretty much every other facet of signaling I've covered these vary railroad to railroad and past to present so I figured I'd compile a guide to railroad number plates (which are distinct from Station Signs).
Beginning with CSX, they use a white on black sign of medium side using a distinctive font that has been pretty consistent since the Chessie era. The number is the milepost in tenths, ie without a decimal point. If there is more than one main track is will be represented by a dash and the track number. Bi-directional signals use an odd-even system with one direction being the nearest odd 10th and the other being the nearest even 10th. The choice of odd-even is not necessarily consistent across an entire line.
CSX also has a compact style that has appeared at various points around the system such as the Trenton Line and former RF&P.
Speaking of Conrail, they used what is perhaps the best number plate system with a whole milepost followed by the track number followed by a directional letter. If there was only a single track the track number 1 would always be used.
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Trenton Line MP 30 Track 1 North |
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PRR Main Line MP 124 tk1 West. Note Conrail letters re-skinned by NS. |
NS honors the former Conrail system on former Conrail territory, but replaces the unit number plates with a modular type, similar to what the original PRR used.
On NS's other territories a milepost in 10ths with no decimal is used with the odd-even system in effect.
Until around 2000, former Southern territory used a large black on white sign and before that bare reflectorized numbers mounted to the mast. Signals not only use the odd-even system, but where there are more than one track, the tracks will use sequential odd or even 10ths creating a spread of 4/10ths per signal location.