| Code | Scarcity |
| HTG | Hard-to-Get |
| VHTG | Very Hard-to-Get |
| Code | Style |
| BBB | Big Big Book |
| BLB | Big Little Book |
| BLBC | Big Little Book Card |
| BTLB | Better Little Book |
| CI | Cast Iron |
| Coco | Cocomalt |
| DA | Dime Action |
| EVW | Engle-Van Weisman |
| FA | Fast Action |
| Gold | Goldsmith Pub. |
| Karmetz | Karmetz Premium |
| Lynn | Lynn Pub. |
| NBTLB | New Better Little Book |
| PU | Pop Up |
| Perkins | Perkins "Kool Aid" Premium |
| Saal | Saalfield Pub. |
| Softcvr | Soft Cover |
| TB | Transition Book |
| TC | Tall Comic |
| TL | Top Line |
| Tarzan | Tarzan Ice Cream Premium |
| Toots | Tootsietoy |
| Wee | Wee Little Book |
| WSP | World Syndicate Pub. |
| Code | Type |
| A | Aviation |
| B | Boys |
| BS | Boy Scout |
| C | Cartoon / Comic |
| CR | Car Racing |
| CU | Circus |
| D | Detective |
| DI | Disney |
| ERB | Edgar Rice Burroughs |
| G | Girls |
| H | Hollywood |
| LT | Looney Tunes |
| M | Military |
| MC | Magic |
| MO | Movie |
| MT | Motorcyle |
| N | Navy |
| SF | Science Fiction |
| SP | Sports |
| SU | Super Hero |
| W | Western |
| ZG | Zane Grey |