I noted in an earlier post here, that the railroads used various classifications for commodities for waybills as noted in the AAR Freight Commodity Classification book. These classifications were important, because they were required by the ICC to report quarterly and annually the movement of such commodities in carloads and tons. You'll find this data in all sorts of industry and government studies and reports.
Does this matter to model railroaders?
Well, not really. No.
Unless you want it to. Then yes.
What my non-committal answer is really saying is that it matters only if it matters to you.
In my case, since I enjoy the historical and research aspects of the hobby, combined with the fact that I am creating waybills for the operation of the railroad, I'd like to gather as much prototypical-type information as I can for that purpose. Since I haven't been able to find a stack of actual waybills for New Britain in my era, I'll need to create that data.
I have data from averaged from the 1950-1954 1% waybill study for commodity traffic originating and terminating in CT. These use commodity classifications, including a number assigned to that commodity.
I have several freight classification books, like this tattered one is from October 25, 1943:
The first one I purchased was a Photo-Reduction Edition from October 1, 1934. This is more 'pocket sized' version, and you can see how much smaller it is than the full version:
I had these before I got the 1% waybill study data, and found I had trouble reconciling the data. In the 1934 version, the commodities don't have any numbers assigned to them. By 1943, each commodity was assigned a number, but they didn't match the numbers listed in the waybill study data.
Then I found a copy of the AAR Freight Commodity Classifications:
I. Products of Agriculture (C.L.)II. Animals and Products (C.L.)III. Products of Mines (C.L.)IV. Products of Forests (C.L.)V. Manufactures and Miscellaneous (C.L.)VI. Forwarder Traffic (C.L.)VII. All L.C.L Freight