This blind was operational from 23rd March 1987. The yellow on black was to denote the 38 was a " tourist route " and the night buses had yellow on black blinds at this time. Oddly the N96 ultimate displays were white on black. Only one of the routes (55) shown operates from Leyton Garage now ( March 2016 )

The yellow displays that were common to BW displays for 55 had  ' tell tale ' to read 38 only

The blind was divided into three groups 38/55 -- 97A/N96 and 230

Taken from Google street view