Aftrer the onslaught of revelations that this thread has contained, I went up to the attic and dug out my copies Greenburgs Guide To LGB and The Official History of LGB. They contain a lot of pretty pictures and lots of information about colour schemes, moulding variations, limited editons for LGB of America etc, but virtually nothing about the transition from Growler to Clam-Shell. Reading between the lines, the vagueness of the text allows a for clamshell without skates to exist, without actually mentioning it!
Maybe it is me, but books of this type about many makes of model trains, nearly always disappoint through the lack of technical detail, coupled with an obsession of having loads of lovely photos of locos, coaches and wagons, but hardly anything else. The worst by far is not either of the above titles but one about Wrenn Railways, which focuses almost entirely on boxes, with no technical details at all! As you may be able to tell, I have a few of these sort of books!
There are some that really made an effort in this area: Michael Foster's 'Hornby Dublo' and Pat Hammond's 'Tri-ang Railways Volume 1' were exceptional. Maybe the time is right for a decent 'all encompassing' history of LGB? There is clearly a lot more information available now, just a case of it being stitched together!
James