The Scale-Craft 4-6-0 and 4-8-4 models were both examined in the new book, but I do have a couple updates based on recent information posted to the American OO scale railroading Facebook group (thank you LCW).  

To the 4-6-0 first, the update there is on the quantity of models produced. I basically just state these were produced in large commercial quantities, but a flyer exists from just before the switch from the DC motor to the AC/DC “Universal” motor in 1939 that sheds more light on this. The flyer offered a special discount on the model (was $26.00, save $10.41!), but the deal was only good “until 4,500 have been sold — regular price after July 30.” What that tells us is that by the middle of 1939, if these are correct numbers, they must have produced more than 4,500 of these, and for sure the overall production was well more than that. How many is hard to guess, but with the version with the Universal motor being more common, could the number be 10,000 or more? No wonder there are so many around! 

Which raises a side question, how many Lionel Hudsons were made? Some similar number? More? What do you think?  

Back to Scale-Craft, the other item is a letter dated April 27, 1950 from Elliott Donnelley, owner of Scale-Craft. He very much had expected to have the 4-8-4 back in production by then. My guess is that it was very close to ready when the line was sold and moved to Hollywood, with many parts produced in the second Libertyville factory before the sale of the line; when he brought Scale-Craft back to Illinois things were in more disarray than he expected they might be. At the time of the letter, he hoped to have the model back out by the end of May, and it would seem maybe a bit longer than that. But come out it did, as the new model was (as noted in the book) reviewed in the November issue of Model Railroader.  

In any case, the total production of the 4-8-4 must be a lot less than the 4-6-0, but both are always models to keep your eyes out for.