That's what I spotted, while working on pictures (and later):
01 Combat Car M1 - could be also armed with .30 AAMG (seen on most photos)
02 Light Tank M2A4 - production began in May 1940 (by Wikipedia) (now 1/35!). It has icon 114 of M5A1 - better would be 98 of M3.
03 Light Tank M3 - has a picture 380 of M3A3. Correct is eg. 27704, 27706, 27008, 27709, 27705 or 27707 (last two are probably M3A1)
08 M4A3 (75) - has a picture 384 of M4A1, with cast hull. This is late version with 47° welded hull - correct is 27726. Same for unit
206 M4A3 (75)(Late)
09 M4A3 (76) - has a picture of M4A1(76), with cast hull. Correct is 27727 or 27733 or 27737
Same for units
135, 189 M4A3 (76)
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SP-Flak:
24 M15-A1 MGMC - has picture of M16. M15 were produced from "early 1943" (Halftrack In Action book) (now: 1/42), M15A1 were yet later.
Would need a change in formation 368 - maybe the earliest would be one of units below:
There could be added
T28E1 - the same, but with unarmoured turret. First vehicles were completed around 11/42 to take part in invasion on Africa.
25 M16 MGMC - produced from 5/43, available probably from a bit later - maybe Sicily invasion (now 1/44)
212 M13 MGMC - has a picture of M16. Accepted in July 1942 according to a Polish book (In Action says mid-42 - now 1/42). (However, the mentioned book suggests, that a production started in 1/43 - it could be verified)
Would need changes in formations 371, 372 - but is there any reason to keep it a separate class (light SPAAV), other, than SP-flak? (It was a direct predecessor of M16 SP-flak). It could be earliest vehicle in SP-Flak class, at 7/42.
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29 LVT(A)4 - should be named LVT-4 (A4 was turreted variant)
30 M29 Weasel - a detail, but a photo shows non-swimming variant (common mistake dating from original SP as well). Swimming variant was named M29C.
33 M3-MG Halftrack - icon 164 of M3A1 halftrack should have a gun ring on a right side.
(34 Scout Jeep - Jeeps with AAMG could be given a separate photo...)
35 Jeep - there was no A/T utility vehicle before Bantam BRC and Willys MA built around 1/41 (now: 1/30)
44 75mm Howitzer - picture 411 is a generic gun, reminding Soviet 76mm, while it should be, I think, M1 howitzer (on old M1 or new M3A3 carriage - I'll attach a proposal drawing basing upon a manual, not very good though)
63 Sniper - it has a picture 32089 (used also for Swedish sniper), showing some SMG with a magazine on the right - same for several other units.
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M3, M6 GMC
78 M3 75mm GMC (class Assault Gun) - photo is T19 105mm halftrack - correct is 27738.
100 M3 75mm GMC (class TD) - photo is T19 105mm halftrack (as above).
They were produced from 9/41 only, and used on Philippines from 12/41 (now: 1/41) (precisely, these early ones were T12 pilot vehicles, M3 were produced from early 1942). Would need changes in some formations, as the earliest unit (M6 should be much later).
Also unit 78 (class Assault Gun) could be made available from 12/41, since they were mostly used in direct support role on Philippines (now: 3/43). It would need changes in some formations, becoming the earliest unit.
211 M6 Fargo - production started only in 4/42 (now 3/41) - it would need change in formations, earliest TD should be 100 M3 GMC.
114 M3 75mm GMC (class Assault Gun) - photo is T19 105mm halftrack - correct is 27738, as above.
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88 P-39 Airacobra - photo 261 is P-63 Kingcobra (used in Soviet OOB primarily). Better one is 14075 (US markings), though it might be P-63 as well.
90 B-25a Mitchell - better photo for level-bomber variant is 30107 (with a glazed nose)
116, 423 75mm M1916 Bty, FG - photo 23015 is Russian M1902 gun (photo is available eg. here
http://en.wikipedia.org/wiki/File:75...SModel1916.jpg )
122 WACO - officially Waco CG-4A
130 Boeing P-26 - better photo is 30262
134 Dodge T214 WC53 - it should rather be named WC51 (on a picture) - WC53 was carryall with closed body, built in a small number.
153, 214 75mm Pack How - it had a single-tail bed (unit 145 has 2111)
188 M4A3 (105) - picture is late variant with HVSS suspension. Better seems 27725 (I think it's 105)
207 M40 155mm GMC - has a picture of M12 GMC. Correct old one is 12037.
(208, 209 4.2in Mort Sect - did there exist M5 and M6 4.2in mortars? I could only find M2
http://en.wikipedia.org/wiki/M2_4.2_inch_mortar
213 Xylophone MRL - photo is some Soviet Katyusha - Xylophone had side-firing racks (however I know, that photos might be scarce). I'll attach a proposal (a model)
240 Light Tank M3A1 - has a picture 380 of M3A3 - correct M3A1 is 27705 (probably) or 27707.
Used definitely longer, than 9/42, though I have no data now.
241 Light Tank M3A3 - according to "Stuart In Action", M3A3 was used by the US forces for training only (most went abroad). Besides, production started in 1/43 (now 10/42), and a better icon is 114 (of M5A1 - it had sloped front)
243 LT M3A3 Recon - should be just M3 - M3A3 was used only for training by US forces, and picture is M3. I don't know however, if M3 were used this way.