Roy,
You are correct. The E/F28 were 600cc side valve machines, and the H/G28 were the OHV (continuation of the OC models.) With foot boards and the touring handlebars, this is likely an E28. Change for drop handlebars and foot pegs, and you would have a F28.
These 600EW are great machines, and I wish mine were as complete (and running) as this one looks to be! But will not fetch as much as the OHV models, understandably.
-Doug