What scale is 'Lion master'?
I wish Lionel would clearly state what is and is NOT'O scale' instead of using ambiguous market labels tht only confuse.
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Lionmaster has always been non scale, its designed to run on smaller layouts
Think Traditional on steroids.
Rusty
The definition of LionMaster is: "detailed, fully-featured engines scaled-down to negotiate O-31 curves and switches".
As far as I know, this definition has never changed in the 10+ years Lionel has been making the LionMaster series.
Jon 
There is no specific scale. Judging from the several I have, generally Lionmaster takes more out of the length than width or height: width and height seem to be adjusted to keep the shortened loco so it looks good. I forget exactly, but I( measured my LM Big Boy a year ago and compared it to a scale model, and basically its a different scale in each dimension: maybe 1/53 in length, 1/50 in height, and close to 1/48 in width, etc.
What Lionel does is make something that looks as "Big Boy" as they can arrange, while able to run on tight radius turns and not-look ridiculous doing so. A scale Big Boy is around 32+ inches long, so you can imagine how ridiculous it would look even if you could fit it to run on O-31. I'm not saying a Lionmaster Big Boy, at about 29 inches, looks good on curves that tight, but on 48" or so it looks fine whereas the scale guy goes not.
Railking (MTH) does roughly the same thing, too.
Lionmaster stuff is pretty nice. I've got the Conrail SD80 power/dummy units and they look great. They're slightly shrunken down to run on smaller curves, but they still seem to look OK with most of my scale freight cars. They still have most, if not all of the details of their full scale legacy diesels, and all the features (sounds, ditch lights, marker lights, number boards, headlights, smoke, etc...).
The nicest thing about Lionels Lionmaster "semi-scale" line is that they are all the same "semi scale" and are evenly scaled down?porportioned from end to end. Semi scale locos from Mth (railking) and K-line tend vary in "semi scale" from loco to loco and certain areas like tenders can be even more "squished" than others.
I still think the Lionel LM Duplex looks a little funny. Maybe it's just me. Still an awesome looking engine, and I'd take one in a heartbeat if it was offered to me. 
The first T-1 Duplex has somewhat undersized cylinders and a larger than necessary gap between engine and tender.
The second release fixed the gap, gave four-chuffs, and added the Legacy Whistle feature.
My T-1 probably has more miles on it than every engine other than my 1950 #2046.
Jon
