| Murals | 593 |
| Museums | 593 |
| Music Arrangers & Composers | 593 |
| Music Instruction-Instrumental | 593 |
| Music Instruction-Vocal | 593 |
| Music Stores | 593 |
| Musical Instruments-Dealers | 593 |
| Music-Background & Foreground | 593 |
| Musical Instruments-Renting & Leasing | 594 |
| Musical Instruments-Repairing | 594 |
| Musical Instruments-Supplies & Accessories | 594 |
| Musicians | 594 |
| Mutual Funds | 594 |
| N |
| Nail Salons | 594 |
| Nailing Machinery | 596 |
| Name Plates | 596 |
| Nannies | 596 |
| Nature Centers | 596 |
| Nautical Instruments | 596 |
| Naval Architects | 596 |
| Neckwear | 596 |
| Neckwear-Whsle & Mfrs | 596 |
| Needlework & Needlework Materials | 596 |
| Negotiation Services | 596 |
| Neon | 596 |
| Nets & Nettings | 596 |
| Network Consultants | 596 |
| News Dealers | 596 |
| News Publications-Trade, Associations, Etc | 596 |
| News Service | 596 |
| Newspaper Distributors | 596 |
| Newspapers | 597 |
| Nightclubs | 597 |
| Notaries-Public | 599 |
| Novelties | 600 |
| Novelties-Whsle & Mfrs | 601 |
| Nurseries-Plants, Trees, Etc | 601 |
| Nursery & Growers’ Equipment & Supplies | 601 |
| Nursery Stock Dealers- Whsle & Growers | 601 |
| Nurses | 601 |
| Nurses Legal Consultant | 601 |
| Nurses’ Registries | 601 |
| Nurses’ Schools | 601 |
| Nurses’ Supplies | 601 |
| Nursing Homes | 602 |
| Nutritionists | 602 |
| Nuts-Edible | 602 |
| O |
| Oakum | 602 |
| Occult Supplies | 602 |
| Occupational Health Services | 602 |
| Occupational Therapists | 603 |
| Oceanographers | 603 |
| Office & Desk Space Rental | 603 |
| Office Buildings | 603 |
| Office Furniture & Equipment- Installation | 603 |
| Office Furniture & Equipment-Dealers | 603 |
| Office Furniture & Equipment-Renting & Leasing | 604 |
| Office Furniture & Equipment-Repairing & | 604 |
| Refinishing |
| Office Furniture & Equipment-Used | 604 |
| Office Furniture & Equipment-Whsle & Mfrs | 604 |