http://www.ama-assn.org/ama1/pub/upload/mm/362/cat3-codes-first-10-yrs.pdf
Page 2 for link above
Main link:
http://www.ama-assn.org/ama/pub/phy...urance/cpt/about-cpt/category-iii-codes.shtml
As for Category II codes:
Level II of the HCPCS is a standardized coding system that is used primarily to identify products, supplies, and services not included in the CPT codes, such as ambulance services and durable medical equipment, prosthetics, orthotics, and supplies (DMEPOS). Because Medicare and other insurers cover a variety of services, supplies, and equipment that are not identified by CPT codes, the level II HCPCS codes were established for submitting claims for these items. The development and use of level II of the HCPCS began in the 1980's. Level II codes are also referred to as alpha-numeric codes because they consist of a single alphabetical letter followed by 4 numeric digits, while CPT codes are identified using 5 numeric digits.
Like CPT, the HCPCS Manual is divided into sections, however, they are not like those in the CPT. They cover such categories as Ambulance Services, Dental Procedures, Injections, Vision Services, and others.
Like CPT codes, National codes are composed of five digits. Unlike CPT codes, HCPCS are alphanumeric. An alphanumeric code combines letters of the alphabet with numbers. In the National codes, one alpha letter is followed by four numbers.
Example: A4550 – Surgical tray
Does this help?