Still got some Folkways 10" and 12" LP's (33.33...rpm); some Stinson 12" which are? transparent and red (difficult to position the stylus as you can see the trackbreakers on the other side). EP's were 45 rpm and around when singles were 10" 78 rpm; I think the 45 rpm singles appeared later. Yes I remember the Topic 8" 33.333rpm too; they didn't have a specific title if I remember. REcord players had two styli: one for the 78's and the other for the 'microgrove' everything else.
Does anyone know how the speeds were arrived at?