After looking at hundreds of diagrams and other data I think I have been able to make some sense of the ATSF class question. As I suspected there were two earlier systems used. If I had some earlier diagram books or class lists I could completely document the first one as well as the other two.
The ICC Symbol list, though appearing in diagram books from 1920 & 1927 appear to have no commonality with anything. Their inclusion is a mystery as I still cant find them in any other roads diagram books or mention of them elsewhere. I also checked some ICC boiler reports, accident reports, boiler inspections lists, and equipment valuations and find no mention of them there either. I am sure they had some purpose somewhere sometime as their way to identify a locomotive type, but must have fallen out of use or never fully adopted.
The last ATSF classification system used is what most everyone is familiar with. Basically, the first road number of a series of locomotives that were the same in design or characteristics was the class for that group. An example would be Class 1 which included locos numbered 1-5 and Class 6 which included locos numbered 6-12. The next Class was 14. Loco number 13 was scrapped 11/1912. With renumbering and dispositions this system was probably quite complicated as well.
The system used previous to this one can be pretty well documented with the materials I have at hand. Using the ATSF 7/1902 General Engine Data list there appears a system using a letter to denote a wheel arrangement. These were as follows- C for 2-8-0, D for 2-10-0, E for 4-4-0, M for 2-6-0, P for 2-6-2, & T for 4-6-0. Noticeably missing were classes for all switchers and the 4-8-0s and possibly others as I didn't dig more beyond here. The switchers were shown 4 WHL or 6 WHL and the 4-8-0s shown 12 WHL. More on those later.
This second system is similar to that used by many roads at one point in time or another. If we look at Class E 4-4-0 we might see E1, E2, etc and then even further subclasses such as E2A, E2B, etc. It got to be very cumbersome as well I am sure, but any road with that many locos is going to have some pains in whatever system is used.
I do not have a way to pinpoint when this second system came into use. Using build dates and diagram revision dates on some diagrams I can conclude the changeover to the last system was probably 1902-1903. I have diagrams revised 8/1902 with the second class still shown and another revised 6/20/1903 with the last system, and others in between. With as many diagrams and other associated paperwork this process must have taken some time. The 4-6-2s & 2-10-2s were built starting in 1903/1904 and they are all in the new system.
There are few clues when the first system came about or when the change to the second happened. The 7/1902 General Engine Description asks some questions that if able to be answered might give some indication. For instance why where there no classifications for all the switchers? How about the 4-8-0s? Diagrams for the switchers give some idea of the class system used. For instance I have diagrams of 0-4-0s classed S4B, 0-6-0s classed S6B through S6I. This makes sense at first glance- 4 wheel or 6 wheel switching locomotives.
Now comes the confusion. A few early 2-8-0 diagrams are showing classes SCA, SCG & SCH. A 4-6-0 diagram was class STA. This was as far as I could go with the early class system.
Hopefully this has been useful. I welcome comments, corrections, additions etc. What was thought to be a quick and easy exercise to add classes to a couple of ATSF digital rosters opened a can of worms that will hopefully add something to history. If anyone could provide copies or scans of diagram books or Descriptions of Locomotives from before 1900 and between 1902 and 1920 they would be very helpful and I would continue to flesh the systems out and perhaps get some better ideas of datings.
Thanks for any help anyone can provide.
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