Mr. and Mrs. David D. O'Neill, wed last Friday, are honeymooning on a Caribbean island, which wouldn't be of widespread interest but for the circumstances of their lives. The wedding was a happy event and a big step forward in society's sensitive adaptation to realities.

O'Neill is a retired District of Columbia firefighter who operates a produce stand at Georgia and Missouri avenues NW.

His bride is Bonnie Davenport, 41, the first and only transsexual officer and a 15-year veteran on the rolls of the Metropolitan Police Department of D.C.

As Ormus W. Davenport III, male, Davenport fathered two children. Five years ago his wife died of cancer. After that tragedy, he went to Colorado and had sex-change surgery, returning to the force in 1979 with an assignment to the same police district -- the 4th, which covers the area north of downtown. (His children are living with grandparents.)

At first, according to Alfred E. Lewis, the veteran Washington Post reporter, Bonnie Davenport suffered snickering among colleagues. But over time, Bonnie earned the same respect that Ormus had won before.

So last week, before the wedding, the macho guys of the 4th District had a prenuptial party for Bonnie Davenport, featuring a cake and, without embarrassment, a very special wedding gift of lingerie.