1959, see above link. O'Day contracted with Marscot till 1960 or 61. You can read some of the history here:
http://www.dolphin24.org/ODay_Corporation.html, but the bottom line is that everyone involved were friends and business partners.
Does
Curlew have wooden or fiberglass seats? and does she have a false keelson forward of the Centerboard case? On my boat (#37), it's an upside-down U-shaped channel of fiberglass, the mast sits on it. I thought it was quite useless till I started using it as an attachment point for under-deck fittings and blocks. These DS's, simple as they may be, are really a gift that keeps on giving. Take good care of your "old girl!"