On Tue, 9 Jan 2018 11:07:06 -0800 (PST), tonbei <
aut...@infoseek.jp>
wrote:
As others have indicated there will be a board with officers' names on
it. Next to each name will be a mark of some sort to indicate whether
the person is "on duty" or "off duty".
So "marked on" is short for "marked as 'on duty'"
This is an example of an ON-DUTY LOCATOR:
https://www.magnatag.com/img/products/ODL/ODLcover.png
It is an illustration of its use in a medical context.
--
Peter Duncanson, UK
(in alt.usage.english)