When we think of vintage IWC center second watches the Cal. 89 springs to mind, but what was IWCs first center second watch?
Cal. 61 IWC's First central seconds watch?
https://www.iwc.com/member/forum/search_all.asp?table=archives&subject=61&sMessage=60&archived=yes&id=68522
The thread, as always, is worth following but for those seeking the answer, see Ralph's reply:
c.61 some information
https://www.iwc.com/member/forum/search_all.asp?table=archives&subject=61&sMessage=60&archived=yes&id=68670
Cheers from the cellar