Diesel Classification scheme?

The other day I was watching a CPR switching move at Whyte Avenue and 102 street, Edmonton AB(*), with the switching locomotive (two unit SD40-2) passing about three feet in front of me. Below the number on the (right) cab-side on one unit (the other was pointing the other way: no sublettering on the left side of its cab) it had
DRF30M / SD40-2
So, how does the CPR's classification scheme for diesels work? "DRF30" I assume means a diesel of 3000 hp for road freight service, but what's M? M-for-modification, because it's a Dash-2, came to mind, but then what did CPR class M630 units? Or is it M for the 13th (or 14th) subclass of 3000 hp freighters (plausible if just about every order of C630M, M630, SD40 and SD40-2 had SOME difference in options specified, I suppose).
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(*) For those not familiar with Edmonton, Whyte Avenue (running east-west) is a major shopping/entertainment street in the southern (Strathcona) part of central Edmonton. The CP line coming up from Calgary ends there: the former passenger station (now a nightclub) is about a block south of Whyte Ave. The yard is basically south of that (tracks fanning out from a point not far from the former passenger station), but one track extends about a block north of Whyte Avenue: when switching a long cut of cars, the switching power pulls across the street. ... Big road-freight power (AC4400/ES44AC) makes it up to about the old passenger station before cutting off and going to "rest" a bit to the East; switching power that I've seen in the past few weeks includes SD40-2 and first generation Geeps.

You pretty well hit it right on the money. The last letter, which should be in lower case, represents the order number for that class. DRF-30m would be SD40-2's 5675-5717. CPR's M630's were also classified as DRF-30. For more information you can refer to the Canadian Classification topic.

Thanks Ken V!
(CN's initials for manufacturers have always amused me, since many U.S. railroads use "E" for EMD and "G" for General Electric: precisely the reverse of CN's usage!)
Do you know if CPR adopted its scheme a year or two earlier than CN? Some of the earlier-adopted U.S. classifications didn't specify manufacturer. PRR, for one, started with a system that didn't, then switched to a scheme with "A" for Alco (which would correspond to CN's "M" for Montreal: I think that the Schenectady-built RS-11 of CN's U.S. subsidiaries got "M" as a prefix, with a final letter marking the fact that they weren't really MLW RS-18), "B" for Baldwin, "E" for EMD, "F" for Fairbanks Morse (would CN have used "C" for Canadian Locomotive Company for its F-M design diesels?), "G" for General Electric and "L" for Lima.

CP's classification system unlike CN's doesn't differentiate between builders. An SD40-2 is the same class as an MLW M630.

Interestingly enough, the CN SD70M-2's don't have any CN classification symbols, they're simply labeled as SD70M-2. Yet the ES44DC's are in the EF-644 class with the Dash 9's.

Thanks again!
With the small number of active locomotive builders, and most of the units being ordered belonging to a small number of models(*), it may be that somebody at CN just forgot the tradition of assigning class designations. Penn Central used the ex-PRR classification system, but by the time Conrail was formed in 1976, management apparently felt there was no need for one: Conrail just used builder's models.

(*) Though, given the number of companies marketing hybrid and Genset units, that could be changing!

ENR3870 wrote:CP's classification system unlike CN's doesn't differentiate between builders. An SD40-2 is the same class as an MLW M630.

Interestingly enough, the CN SD70M-2's don't have any CN classification symbols, they're simply labeled as SD70M-2. Yet the ES44DC's are in the EF-644 class with the Dash 9's.

Some do.. but they're slow coming. They are the GF-643 class, along with the SD 75's. I've seen a few come through. The original 8000-8024 series seem to have the class markings (specifically, GF-643d) more often than the 8800's do (GF-643e), probably to do with the retrofits they've received and having spent time in a shop somewhere..

The G is for General Moters Diesel Division, not EMD.