What must practitioners prominently display regarding the equipment used for microdermabrasion?

Practitioners must prominently display the manufacturer's certificate of training proficiency because it serves as proof that the practitioner has completed necessary training and is qualified to operate the microdermabrasion equipment safely and effectively. This certification ensures that the practitioner adheres to the standard practices and safety protocols associated with the use of such equipment, thereby protecting both the client and the practitioner.

Displaying this certificate is crucial for establishing trust with clients, as they can see that the practitioner is not only knowledgeable but also compliant with industry standards. It reflects a commitment to professionalism and the delivery of safe services, which is essential in a field that involves skin treatment procedures.

The other options, while they may hold some relevance in specific contexts, do not directly address the qualifications related to the safe and effective use of microdermabrasion equipment. The purchase receipt provides a record of transaction but does not demonstrate skill or training. A price list is informative but does not contribute to the safety or quality of service provided. Client testimonials might indicate satisfaction but do not verify the practitioner's qualifications.