Here's a scan from my copy of the Scarth / Reeves design for the Stirling Single. They're old drawings and I know that Reeves updated and improved them later. It's not clear to me if the OD is over the tread or the flange. No idea what "edge wheels" refers to.
To complicate things a little, the loco. side elevation, drg. no. 1, gives wheel diameters, showing the trailing wheel as 4 13/16" over the tread. Take yur pick! HTH.
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Edited By Clive Brown 1 on 05/07/2022 09:06:46