Class L1 (Locobase 3093) 
Data from [external link] for the original 1917 railroad diagrams. See also DeGolyer, Volume 40, pp. 36+ and "Mikado Locomotives, Chicago Great Western", Railway Master Mechanic (September 1912) , p. 419-420. Works numbers were 37965-37970, 37985-37988 in June 1912.
Firebox heating surface included 31.4 sq ft (2.9 sq m) of "water tubes." A later upgrade added 81 sq ft (7.25 sq m) of thermic syphons, which is reflected in the specs. By this time, the piston valves were a healthy 15" (381 mm) in diameter.
These Mikes were an instant success on the CGW, which conducted tests in March 1914 tests among ten each of the CGW's Consolidations, Prairie Mallets, and the Mikados over the Eastern Division between Oelwein, Iowa and Stockton, Ill. The results, according to Railway Age (30 October 1914), proved the value of the superheater and of the 2-8-2 wheel arrangement in general. Mikes handled more tonnage, compiled more gross ton-miles and cost less to run per mile.
Ten more L-1a, which were essentially repeats of the L-1, were supplied by Baldwin in 1920 (see Locobase 6124). Six L-1bs (733, 735-739) were L-1s (nee 703, 705-709) with disk main drivers, mechanical stokers, and new frames; they were rebuilt at Oelwein in 1937-1939; see Locobase 6125. The last Mikado went out with steam in 1950.
Class L1A (Locobase 6124)
Data from 1943 Chicago Great Western diagram book provided by Allen Stanley from his extensive Rail Data Exchange in March 2004. See also DeGolyer, Volume 67, pp. 191+. Works numbers were 53439-53470 in July; August 53511-53513, 53531, 53567-53568, 53614 in August; and 53694 in September.
Firebox heating surface included 31.4 sq ft (2.9 sq m) of "water tubes." Piston valves were a healthy 15" (381 mm) in diameter.
These were repeats of the 1912 L-1s (Locobase 3093) and, except for a slight reduction in tube heating surface, essentially identical. Like the L-1s, these carried on in freight service until the end of steam on the CGW in some cases.
Class L1B (Locobase 6125)
Data from 1943 Chicago Great Western diagram book provided by Allen Stanley from his extensive Rail Data Exchange in March 2004.
Firebox heating surface included 81 sq ft (7.5 sq m) of thermic syphons. Piston valves were 15" in diameter.
This quintet (built as 703, 705-709) was born again at Olewein with new frames, mechanical stoker (hard to believe the crews had served 70 sq ft by hand until then!), and disk main driver on the third axle.
Class L1s (L2) (Locobase 4178)
See [external link] for the original 1917 railroad diagrams. See also DeGolyer, Volume 55, pp. 30+. Works numbers in 1916 were March 43096-43099; April 43190-43193; and May 43290-43291
Firebox heating surface includes 39 sq ft (3.6 sq m) in four arch tubes; later on the shops added thermic syphon; see Locobase 9464.. Similar to the earlier Baldwin Mikes delivered to this road, this class had a combustion chamber, and consequently less superheating surface. This was offset to some extent by an increase in firebox heating surface.
Three L2 became L2B in the 1930s. Although Drury (1993) doesn't say specifically, it's likely that the redesignation reflected the same refit as the L1 class. (That refit had disk drivers, new frames, and a mechanical stoker.) Like the earlier class, these served satisfactorily until the end of steam.
Class L2B (Locobase 9464)
Data from 1943 Chicago Great Western diagram book provided by Allen Stanley from his extensive Rail Data Exchange in March 2004.
The date on this entry reflects the second rebuilding of three -- 710, 712, 716 -- of this 1912 design (for the original, see Locobase 4178). In 1929, the CGW rebuilt the firebox by adding 98 sq ft (9.1 sq m) of thermic syphons and increasing the direct heating surface by 33%. Piston valves measuring a relatively large 15" in diameter (381 mm) distributed steam to medium-sized cylinders.
Class L3 (Locobase 6127)
Data from 1943 Chicago Great Western diagram book provided by Allen Stanley from his extensive Rail Data Exchange in March 2004. See also DeGolyer, Volume 58, pp. 83. Works numbers were 50672, 50729-50731 in November 1918 and 50777-50781, 50803 in December.
Firebox heating surface included 98 sq ft (9.1 sq m) of thermic syphons and 27 sq ft (2.5 sq m) of arch tubes. Piston valves were 14" (356 mm) in diameter.
A few of the 625 USRA light Mikados made it to the CGW where they performed capably for two or three decades. Along the way, the firebox was slightly modified as shown in specs to include the thermic syphons, a practice that the railroad seems to have applied to most of its locomotives.
The first of the L-3s left service in 1939; the last saw steam out in 1950.
