Assertion: green chalkboard | /r/AtLocation | 1960
Facets:
Source sentences:
text: Green chalkboards, generally made of porcelain enamel on a steel base, first appeared in the 1960s.
text: Green chalkboards, generally made of porcelain enamel on a steel base, first appeared in the 1960s.
text: Green chalkboards, generally made of porcelain enamel on a steel base, first appeared in the 1960s.