Green’s Dictionary of Slang

(US campus) a devotedly hard worker, a taskmaster.

1960		A. Buzo Front Room Boys Scene i: thomo: All right, you blokes, let’s get on with the work, eh? jacko: Righto, Thomo, righto. You’re a bit of a conch this morning, aren’t you? thomo: Well, there’s work to be done.
1980		L. Birnbach Official Preppie Hbk 90: 13 Words For The Person Who Is Working — 1. Grind 2. Squid 3. Pencil Geek 4. Cereb 5. Grub 6. Weenie 7. Throat 8. Tool 9. Wonk 10. Gome 11. Nerd 12. Spider 13. Conch.