I have not located a high quality scanned version of a turn of the century Southern coach floor plan. For a stand-in, I’ve attached a reduced resolution scan of Southern drawing 2-B-9 drawn March 6, 1896 of a “65’Combination Pass Car”. (I recall the original linen is what the scan was made from.)

A characteristic of drawings of the period was they described cars a drawing referred to only by the length of the car, not individual car numbers. That can be a problem because all 65’ P&Bs were not the same. I’ve included a small snippet from a passenger car data base (10,841 total entries). Note the date range (probably estimates when ther ICC Val study was done, recirds from 1865 probably never made to the Southern's files). Even this small sample of cars probably came from different predecessor railroads and car builders. We have no way of knowing which of these cars the drawing represented.

Sou	573		12/31/24	P&B all wood 43' 0" M&B 1870
Sou	575		01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	578		01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	579		01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	580		01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	581		01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	582			P&B all wood 65' 0" various builders 1865-1901
Sou	582			P&B all wood 65' 0" various builders 1865-1901
Sou	585	600	01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	586			P&B all wood 65' 0" various builders 1865-1901
Sou	587	602	01/01/28	P&B all wood 65' 0" various builders 1865-1901
Sou	575	604	06/30/24	passenger & baggage (under 70’)

Actually, the drawing may NOT have represented ANY cars the Southern owned. During this period, the Southern produced its own car design drawings and sent them to carbuilders for quotes. The design could have changed, or been replaced alltogether with a selected builder’s design. Here’s the drawing…..

Your basic question is really (!) hard to answer…how were the cars numbered?

The answer needs to start by reminding everyone that in 1900, the Southern’s rolling stock was a conglomeration of many railroads equipment from the Richmond Terminal bankruptcy.

The ICC Valuation study attempted to include as-built or prior car numbers IF they were known.

The following is a digital photo of a page from ledgers I borrowed from the SE Railroad Museum (Atlanta Chap, NRHS) years ago. (Originally from Pegram Shop, donated by Mr. Bill Purdy, I believe). It is also from the ICC Val Study and provides whatever data that was available, or could be estimated. Note the three left columns, the third shows “system numbers”, those represent the new Southern system. Hard to read but the second column shows some prior numbers. (Note to Jason Greene, I’d like to see someone make good quality scans of those ledgers before they fall apart, I only had access to them for a few days, thus the photos.) 

In general we can say around 1900, Southern P&Bs were numbered in the 500 and 600 series, full coaches were in the 600,  series and continued up from there into the 1300s and 1400s by thge 1920 and 30s.

Ike