"Blackbird" was the moniker for the SR-71. I've never heard of the SR-77. Either you have information on a super secret skunk works project, or else I suspect you might be taking the mickey out of the editors of the article for their SR-1 typo?
At some point, in a speech or introduction, some high ranking official misread that as SR-71, and after that all documentation was updated to show this new designation.