Dominion Collecting and Detective Agency, New Brunswick, 1893 Postmarked Cover

There's an ephemera dealer with a small outpost at an antiques shop i frequent in southern Maine who I can always count on for some little interesting thing--and how not to be intrigued by the activities of the Dominion Collecting and Detective Agency??? Postmarked 1893, I'd like to think it once contained evidence of some very sleuthy detective work, conducted on behalf of a a Mr. J.L. Cain of Montville, Maine! Who knows, but a fun thing, with a very film noir sort of feel, though of an earlier era, and what an excellent name "Dominion" for a detective agency.

 9 3/8" x 4 1/8" and in good condition, empty now, with a few tears to the reverse, no matter.