Overland Models imported a 2-rail O scale 2-8-4 for various roads.
As with several OMI models, it had a cast "white metal" frame. Several
of these frames have rotted. I don't know when those models were
produced, nor where they were made. The 2-rail O scale SP GS-4s that
OMI imported in the early 80s (I have two) are fine.

In late 90s Weaver produced several troop sleepers in O scale (both
2- and 3-rail). They used a 'white metal" frame, many of which have rot.

--
Rod Miller
Handcraftsman
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Custom 2-rail O Scale Models: Drives, | O Scale/S Scale West/Narrow Gauge West
Repairs, Steam Loco Building, More | 2019 O Scale National Convention
http://www.rodmiller.com | 2019 Dates Are May 23 - 25
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