These are now called "Monograms".
| Prefix | Object | Application |
|--------|--------|-------|
| A | | |
| B | Buildable | Harbormaster |
| C | Countdown | Countdown |
| D | Revision | Diffferential
| E | Event | Calendar |
| F | File | Files |
| G | Graph | Facts |
| H | Herald Rule | Herald |
| I | Initiative | Fund |
| J | | |
| K | Key | Passphrase |
| L | Document | Legalpad |
| M | Mock | Pholio |
| N | Nuance Item | Nuance |
| O | Package | Owners |
| P | Paste | Paste |
| Q | Question | Ponder |
| R | Commit/Repository | Diffusion |
| S | Space | Spaces |
| T | Task | Maniphest |
| U | URL | Phurl |
| V | Vote | Slowvote |
| W | Widget | Dashboards |
| X | | |
| Y | Pull Request | Releeph |
| Z | Thread | Conpherence |
| @ | User | People |
| # | Project | Projects |