I looked and could not find any electric start Sportwin from 59. I did not talk directly to the owner, just got a voicemail saying "I have a 1959 Sportwin electric start 10 hp motor. What can I get for it?"
It looks as though the 10hp and the 18ph used the same cowl, so something likely got switched along the way. A wolf in sheep’s clothing!
This one calls for more follow up and to look at it in person. I will let you guys know what I find. May be a couple days, but I will reply.
Thanks.