I have received this question several times this past week, so here's the answer...
What is a "Zed" Card?
A comp card (also called composite card, z card, sed card or set card) is a marketing tool for actors and especially models. They serve as the latest and best of a model's portfolio and are used as a business card.
A Z-CARD is also a folded leaflet format, typically used for marketing communications campaigns for example a loyalty programme or seasonal promotion.
Peter Marlowe in London invented models composites in 1965, then printed on paper to an A4 format. The format was changed in 1972 to an A5 card format, for filing purposes, and a few other companies started publishing cards for the model industry under different trade names since Peter Marlowe had registered the Trade Mark "Model Composite" in Europe and the USA.
Amongst these was Sebastian Sed who traded under the name Sed Cards, which are sometimes mis-pronounced as Z ("Zed") or Set cards. The publishing house of Marlowe Press stopped trading in 1990 and the words "models composites" and "comp cards" became generic within the model industry. Comp card databases and creation tools have moved online in recent years.
History and origination of the Comp Card: http://www.modelscomposites.com/press3.htm
If you are primarily an ACTOR who wants to do some modeling - you need a HEADSHOT. Actors can get print work from headshots
If you are primarily a MODEL who wants to do a few commercials, you need a COMP card. Models can get commercials with a comp card - BUT you will also need a professional RESUME with the details of your experience.
How to write a resume: http://www.actorsinfobooth.com/resources/how-to-write-a-resume
Sample Resume: http://www.actorsinfobooth.com/resources/sample-resume