This was a matter of considerable discussion, and consternation, throughout the Russell period and well into and through the Rutherford period.
Basically, Russell saw the selection of the anointed as being "when you're 'called by God,' you are thereby chosen, and automatically of the anointed"...thence beginning the 'proving' period during which you ultimately demonstrate your faithfulness to the calling and choosing--this led to the emphasis on "character development," (an individual experience and course of life, measured by individual consequences).
Rutherford characterized the 'confirmation' of truly being of the anointed in terms of 'what one did' to prove that they were actually of the anointed class to begin with, and if they didn't conform to the directions from the organization, then, by default, they thereby manifested that they were never actually of the anointed (an individual experience, measured by organizational consequences). (1 John 2:19)
Over the last 50 years, the WTS has always maintained that the validity of asserting "I'm of the anointed" is a statement that goes beyond the bounds of any human to pass certain judgment. Therefore, even though the 'influx' of anointed ones at certain times (for example, during the expansions of the WTS into South American and South African cultures) has been superficially explained away as residual emotional effects of the Babylonish religions from which such claimants derived, nevertheless it's basically a "hands-off" policy.
As a personal experience, I knew a "young one" of the anointed, from my brief period in Palmdale, California. Dan Foley (sp?) was at Bethel in the late 60s, and became the Ministry School Overseer at the Brooklyn Heights congregation, and, one evening, as I stood in the back of the Brooklyn KH, he gave Fred Franz a "W" on one of Fred's talks! Everybody laughed. Dan ended up leaving Bethel, to serve as a special pioneer in one of the New England areas. Word was that he'd found Bethel unfulfilling to his "call." I paid him $5 for the glass top to his work desk.