Duncan Electric (Manufacturing) Co. (1901-1975)
| DC | Singlephase | Polyphase | Switchboard | Rotating standards |
| A | ||||
| D | D | C, F | ||
| E, EA | M | R, FR | ||
| ER | M1 | MS | ||
| M2 | M2P | M2 series | ||
| EK | MD | MD | MD | |
| MFS, MFA | MF | MF-W | ||
| MG | MG-W | |||
| MH | MH-W | |||
| MKS, MKA | ML |
For more information on later Duncan meters (1960-1975), Landis & Gyr (1975-1998), and Siemens PTD meters, refer to the modern meters section.