Common sense comes into play here regarding clarity of the common usage of 'c.' for circa it boils down to placement in most circumstances. If one sees a 'c.' before as in: c. 15th (and most likely that above would be followed by the word - century) it would certainly be clear that it was meant to be circa. Who would take the 'c.' in that example for anything other than 'circa.' If after, as in: 15th c., it would certainly refer to century in this example. Why would one ever use that last example to mean '15th circa' which simply doesn't make sense. ========================================================= Important Subscriber Information: The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes). If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).