Both 3-truck shays have the same engine # and logo they look very close in detail however the Spectrum ON30 is 35% smaller overall than the 3-truck MTH Premire Shay. THe same dimensional difference holds true for the Heisler, however, the O-scale version is a Lionel, so that may be a poor comparison for "scale" size.
It looks as if Spectrum either reduced the dimensions proportionately to "fit" or MTH/Lionel/Weaver increased the size to better fit the O-scale track. I just wondered which way it went. The MTH premire shay and climax does say 1:48, hence the confusion in my noggin.
Don't know if I will actually utilize the ON30s, they are very nice and NIB, but I am not sure about mixing scales, especially since I have "O-scale" (lionel may shoot a hole in the O-scale) versions of 3 out of 4 of these already.
Does anyone mix scales at different distances or elevations for perspective? Just wondering how you square that when the locomotives eventually come close to one another.
Just curious. I actually ponder stuff like this more often than I care to admit. For instance, when did worms become good bait for fish? Worms live in the ground and fish don't. It is not as if they ever crossed paths often before someone stuck one on a hook.