Truly this is a question that cannot be answerd because the watchtower keeps changing who the 144000 are...
One of the core doctrines of the Watchtower is that only 144,000 humans will go to heaven, where they are to rule as kings. Most Jehovah's Witnesses are not considered part of the 144,000 and do not expect to go to heaven. Rather they believe themselves part of the Great Crowd that will never die, but rather reside forever on earth.
Prior to 1935, all "true Christians" were said to be anointed and called to heaven. Therefore, everyone associating with the Watchtower Society prior to 1935 was automatically part of the heavenly class. Those who converted after 1935 generally are told they have an earthly hope.
Russell had said that all 144,000 had been chosen by 1881 and presented a number of Biblical reasons why this was the case.
Remember, too, that the Scriptures proved to us in various ways-by the Jubilee Cycles, the 1335 days of Daniel, the Parallel Dispensations, etc.-that the "harvest" or end of this age was due to begin in October, 1874, and that the Great Reaper was then due to be present; that seven years later-in October, 1881-the "high calling" ceased, though some will be admitted to the same favors afterward, without a general call being made, to fill the places of some of the called ones who, on being tested, will be found unworthy.
Thy Kingdom Come p.362
"And the three and a half years following the Spring of A.D. 1878, which ended October, A.D. 1881, correspond to the three and a half years of continued favor to individual Jews in the last half of their seventieth week of favor. As in the type that date-three and a half years after the death of Christ-marked the end of all special favor to the Jew and the beginning of favor to the Gentiles, so we recognize A.D. 1881 as marking the close of the special favor to Gentiles-the close of the "high calling," or invitation to the blessings peculiar to this age-to become joint-heirs with Christ and partakers of the divine nature." The Time Is At Hand 1916 ed. p.235
Rutherford recycled this concept, and without any Biblical basis moved the sealing of the 144,000 from 1881 to 1931.
"God having a fixed time for every purpose (Ecclesiastes 3:1), his time to give creatures on earth the opportunity to get in line for a heavenly reward has been from A .D. 29 until,chiefly,1931,called the "dayof salvation". "Let God be True" 1946 ed. p.298
"Although Jehovah had come to his temple in 1918 and had begun judgment of this anointed class, still others must be brought in, because some were found unworthy and theymust be replaced. The evidences show that this continued until especially 1931, when there began a work of gathering those recognized as "other sheep" of the Lord Jesus Christ." Jehovah's Witnesses In The Divine Purpose 1959 p.139
This was later changed to 1935.
"Hence, especially after 1966 it was believed that the heavenly call ceased in 1935." Watchtower 2007 May 1 p.30
"Their being identified in 1935 as the great crowd of other sheep was an indication that the choosing of the 144,000was then about complete." Revelation, Its Grand Climax Now at Hand p.125
In recent years, those that chose to partake of the emblems have been criticised as having emotional issues.
"Over the years some, even ones newly baptized, have suddenly begun to partake. In a number of cases, after a while they acknowledged that this was an error. Some have recognized that they partook as an emotional response to perhaps physical or mental strain. But they came to see that they really were not called to heavenly life. They asked for God's merciful understanding." Watchtower 1996 Aug 15 p.31
These comments a reminiscent of the words of Jesus at Matthew 23:13:
"Woe to you, teachers of the law and Pharisees, you hypocrites! You shut the kingdom of heaven in men's faces. You yourselves do not enter, nor will you let those enter who are trying to."
In 2007 this teaching was once again changed, with the admission that the Bible does not give a date for when the closing would occur.
"As time has gone by, some Christians baptized after 1935 have had witness borne to them that they have the heavenly hope. Thus we cannot set a specific date for when the heavenly hope ends." Watchtower 2007 May 1 p.31
And once again even these "facts" may need updated .... so again you question has an ever changing answer ...