| Abbreviation | Definition |
|---|---|
| MR | Morgans Foods, Inc. |
| MRIA | McRae Industries, Inc. Class A |
| MRIB | McRae Industries, Inc. Class B |
| MRM | Merrimac Industries, Inc. |
| MRS | Midcoast Energy Resources, Inc. |
| MRTG | Multi Router Traffic Grapher |
| MRY | Memry Corporation |
| MS | Milestone Scientific, Inc. |
| MSI | Movie Star, Inc. |
| MSL | MidSouth Bancorp, Inc. |
| MSN | Emerson Radio Corporation |
| MSS | Measurement Specialties, Inc. |
| MSW | Mission West Properties, Inc., of Maryland |
| MTT | Merrill Lynch & Company, Inc. |
| MTY | Marlton Technologies, Inc. |
| MWH | Baycorp Holdings, LTD. |
| MXC | Matec Corporation of Maryland |
| MXM | Maxxam, Inc. |
| MYE | Myers Industries, Inc. (de-listed - moved to NYSE) |
| NAT | Nordic American Tanker Shipping Company |