Thanks everyone. There were 19 responses from accounts with more than 50 posts. I wrote these in order, then used pickerwheel.com to generate a random number. The first winner had their account here set for "Does not wish to receive email," so I eliminated that entry and generated another number. The winner then was Coastwatcher—congrats. An email has been sent.
Not stated in the original offer is that there is a fifth cover, endorsed "Per S.S. Olympic," which was a sister ship of the Titanic. I'm keeping that one for myself, but thought others might enjoy knowing about the brush with history there.
Please, for any of these giveaways, if you enter, be sure you have 50 quality posts on the forum, and that your account is set to accept email.