This must be Optimus Princeps free font by Manfred Klein which is actually similar to Trajan by Carol Twombly (1989).
I don't know if this should be considered a plagiarism or just a different interpretation of the Roman Square Capitals found in Trajan's Column.

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I found it using Find my Font - http://www.findmyfont.com

It's hard to say whether Optimus Princeps was derived from the outlines of Adobe Trajan. If not, it's totally OK; if so, it's totally not OK.

hhp