There were more than 2 classes. This is a summary of "the classes" as presented in "The Finished Mystery" (1917), p. 575-6:
The Classes. — In the Kingdom there will be several distinct classes, according to opportunity and degree of faithfulness in ages preceding establishment of the Kingdom.
The priests will be the glorified Little Flock, faithful unto death, sons of God, the Righteous One (Zadok, righteous), who during the Gospel Age "kept the charge of God's Sanctuary," by faithfulness to the Word of God at any cost. They will be "of the Divine nature." — Ezek. 40:44-46; 43:18-27; 44:15-31; 45:4; 48:10-12.
The antitypical Levites (Great Company), will have spirit nature akin to the angelic, because though during the Gospel Age they were also begotten of the Spirit, sons of God (Zadok, righteous), they "went astray from God, after their idols;" they ministered unto the people before their idols and caused the house of Israel (Christendom) to fall into iniquity. They shall hear their iniquity." — Ezek. 44:10-14; 45:5; 48:13-14.
The Ancient Worthies (the Prince), who in the Jewish Age were faithful unto death amid incredible trials of faith (Heb. 11), will during the 1,000 years be of the perfect human nature, and will be on earth the visible leaders and rulers of mankind. — Ezek. 44:1-3; 45:7-17, 21-25; 46: 16-18; 48:21-22.
The servants of the city will be of the perfect human nature, and engaged in the multifarious duties of a world wide government. They will be taken from amongst mankind. Some are spoken of as servants and some as sons of the Ancient Worthies. — Ezek. 48:18-19; 46:16-18.
The people of the Kingdom will be first the resurrected Hebrews, making progress during the 1,000 years toward human perfection, but who in previous ages had not been consecrated, to God and had been far astray from Him. (Romans 1.) — Ezek. 43:7-9; 44:6-12, 15, 19, 23-30; 45:6-21; 46:1-3, 9-10; 47:13-14; 48:11,18-19, 23-29.
The "strangers" will be the resurrected billions of humanity, not Jews, who gaining the heart circumcision of a conscience cleansed by the blood of Jesus, shall be as though born to the same conditions as the Hebrews. None of them shall have part in the direct service of God. — Ezek. 44:9; 47:22-23; Zech. 14:20-21; Numbers 31:47; Joel 3:17; Joshua 9:22-27; Rev. 21:27. - http://www.strictlygenteel.co.uk/finishedmystery/fme40-48.html
In 1931/2 (source: the "Vindication" series), the 3 main classes were,
Heavenly
the Little Flock, royal, co-heirs, Christ/anointed class;
The Great Company/Multitude who were originally spirit-anointed but became spiritually negligent and had to undergo the great tribulation to get to serve in the heavenly temple;
Earthly
The Jonadabs, who were still part of Satan's organization but not sympathizers with it. They were the 'sighing and groaning' ones. In the early '30s they were encouraged to become consecrated or dedicated to the Lord.
In 1935, at that momentous Convention, Rutherford merged the Great Multitude class with the Jonadab class and gave them an earthly hope. Hey presto! 2 classes.