I have always found the notion of "Modernism" (typically dated from 1920's-1970's) to be, at least to me, ill defined. That was why I found it compelling that "The London Festival of Architecture 2015" was showcasing an exhibition of modernist toys from the 1960's by "London studio Systems." It looks to me like the defining principle is simplicity of line and the use of natural materials. What is your impression?
"Duck" 1993 Mark Ryland
"Balancing Troupers" 1963 by Fredun Shapur and Kurt Naef
Locomotive Toy 1937 Marx Company